Time-multiplexed display of virtual content at various depths

ABSTRACT

Techniques for operating an optical system are disclosed. World light may be linearly polarized along a first axis. When the optical system is operating in accordance with a first state, a polarization of the world light may be rotated by 90 degrees, the world light may be linearly polarized along a second axis perpendicular to the first axis, and zero net optical power may be applied to the world light. When the optical system is operating in accordance with a second state, virtual image light may be projected onto an eyepiece of the optical system, the world light and the virtual image light may be linearly polarized along the second axis, a polarization of the virtual image light may be rotated by 90 degrees, and non-zero net optical power may be applied to the virtual image light.

CROSS-REFERENCES TO RELATED APPLICATIONS

This application is a continuation of International Patent ApplicationNo. PCT/US2020/013130 filed Jan. 10, 2020, entitled “TIME-MULTIPLEXEDDISPLAY OF VIRTUAL CONTENT AT VARIOUS DEPTHS,” which claims the benefitof and priority to U.S. Provisional Patent Application No. 62/791,441,filed Jan. 11, 2019, entitled “TIME-MULTIPLEXED DISPLAY OF VIRTUALCONTENT AT VARIOUS DEPTHS,” the entire disclosures of which are herebyincorporated by reference, for all purposes, as if fully set forthherein.

BACKGROUND OF THE INVENTION

Modern computing and display technologies have facilitated thedevelopment of systems for so called “virtual reality” or “augmentedreality” experiences, wherein digitally reproduced images or portionsthereof are presented to a user in a manner wherein they seem to be, ormay be perceived as, real. A virtual reality, or “VR,” scenariotypically involves presentation of digital or virtual image informationwithout transparency to other actual real-world visual input; anaugmented reality, or “AR,” scenario typically involves presentation ofdigital or virtual image information as an augmentation to visualizationof the actual world around the user.

Despite the progress made in these display technologies, there is a needin the art for improved methods, systems, and devices related toaugmented reality systems, particularly, display systems.

SUMMARY OF THE INVENTION

The present disclosure relates generally to techniques for improving theperformance and user experience of optical systems. More particularly,embodiments of the present disclosure provide systems and methods foroperating an augmented reality (AR) device comprising adaptive lensassemblies and/or shutter elements for displaying virtual content atvarious depths. Although the present disclosure is described inreference to an AR device, the disclosure is applicable to a variety ofapplications in computer vision and image display systems. A summary ofthe present disclosure is provided below in reference to a series ofexamples.

Example 1 is a method of operating an optical system, the methodcomprising: receiving, at the optical system, light associated with aworld object; linearly polarizing, by a world-side polarizer of theoptical system, the light associated with the world object along a firstaxis; when the optical system is operating in accordance with a firststate: rotating, by a world-side switchable waveplate of the opticalsystem, a polarization of the light associated with the world object by90 degrees; linearly polarizing, by a user-side polarizer of the opticalsystem, the light associated with the world object along a second axisperpendicular to the first axis; applying zero net optical power, by alens assembly of the optical system, to the light associated with theworld object; when the optical system is operating in accordance with asecond state: projecting, by a projector of the optical system, lightassociated with a virtual image onto an eyepiece of the optical system;outcoupling, by the eyepiece, the light associated with the virtualimage toward the user-side polarizer; linearly polarizing, by theuser-side polarizer, the light associated with the world object and thelight associated with the virtual image along the second axis; rotating,by a user-side switchable waveplate, a polarization of the lightassociated with the virtual image by 90 degrees; and applying non-zeronet optical power, by the lens assembly, to the light associated withthe virtual image; wherein the optical system is operating in accordancewith the first state when the world-side switchable waveplate iselectrically activated and the user-side switchable waveplate is notelectrically activated; wherein the optical system is operating inaccordance with the second state when the user-side switchable waveplateis electrically activated and the world-side switchable waveplate is notelectrically activated; wherein the world-side polarizer is coupled tothe world-side switchable waveplate; wherein the world-side switchablewaveplate is coupled to the eyepiece at a world side of the eyepiece;wherein the user-side polarizer is coupled to the eyepiece at a userside of the eyepiece; wherein the lens assembly is coupled to theuser-side polarizer; wherein the user-side switchable waveplate ispositioned between two layers of the lens assembly.

Example 2 is an optical system comprising: a world-side polarizerconfigured to linearly polarize light associated with a world objectalong a first axis; a world-side switchable waveplate coupled to theworld-side polarizer and configured to rotate a polarization of thelight associated with the world object by 90 degrees when the opticalsystem is operating in accordance with a first state; an eyepiececoupled to the world-side switchable waveplate; a projector configuredto project light associated with a virtual image onto an eyepiece whenthe optical system is operating in accordance with a second state; auser-side polarizer coupled to the eyepiece and configured to: linearlypolarize the light associated with the world object along a second axisperpendicular to the first axis when the optical system is operating inaccordance with the first state; and linearly polarize the lightassociated with the world object and the light associated with thevirtual image along the second axis when the optical system is operatingin accordance with the second state; a lens assembly coupled to theuser-side polarizer and configured to: apply zero net optical power tothe light associated with the world object when the optical system isoperating in accordance with the first state; and apply non-zero netoptical power to the light associated with the virtual image when theoptical system is operating in accordance with the second state; and auser-side switchable waveplate positioned between two layers of the lensassembly and configured to rotate a polarization of the light associatedwith the virtual image by 90 degrees when the optical system isoperating in accordance with the second state.

Example 3 is a method of operating an optical system, the methodcomprising: receiving, at the optical system, light associated with aworld object; linearly polarizing, by one or more world-side shutterelements of the optical system, the light associated with the worldobject along a first axis; when the optical system is operating inaccordance with a first state: rotating, by the one or more world-sideshutter elements, a polarization of the light associated with the worldobject by 90 degrees; linearly polarizing, by one or more user-sideshutter elements of the optical system, the light associated with theworld object along a second axis perpendicular to the first axis; whenthe optical system is operating in accordance with a second state:projecting, by a projector of the optical system, light associated witha virtual image onto an eyepiece of the optical system; linearlypolarizing, by the one or more user-side shutter elements, the lightassociated with the world object and the light associated with thevirtual image along the second axis; and rotating, by the one or moreuser-side shutter elements, a polarization of the light associated withthe virtual image by 90 degrees.

Example 4 is the method of example(s) 3, further comprising: applyingzero net optical power, by a lens assembly of the optical system, to thelight associated with the world object when the optical system isoperating in accordance with the first state.

Example 5 is the method of example(s) 3, further comprising: applyingnon-zero net optical power, by a lens assembly of the optical system, tothe light associated with the virtual image when the optical system isoperating in accordance with the second state.

Example 6 is the method of example(s) 3, further comprising:outcoupling, by the eyepiece, the light associated with the virtualimage toward the one or more user-side shutter elements when the opticalsystem is operating in accordance with the second state.

Example 7 is the method of example(s) 3, wherein the one or moreworld-side shutter elements includes: a world-side polarizer; and aworld-side switchable waveplate.

Example 8 is the method of example(s) 7, wherein the one or moreuser-side shutter elements includes: a user-side polarizer; and auser-side switchable waveplate.

Example 9 is the method of example(s) 8, wherein the optical systemincludes a lens assembly.

Example 10 is the method of example(s) 9, wherein the optical system isoperating in accordance with the first state when the world-sideswitchable waveplate is electrically activated and the user-sideswitchable waveplate is not electrically activated.

Example 11 is the method of example(s) 9, wherein the optical system isoperating in accordance with the second state when the user-sideswitchable waveplate is electrically activated and the world-sideswitchable waveplate is not electrically activated.

Example 12 is the method of example(s) 9, wherein the world-sidepolarizer is coupled to the world-side switchable waveplate.

Example 13 is the method of example(s) 9, wherein the world-sideswitchable waveplate is coupled to the eyepiece at a world side of theeyepiece.

Example 14 is the method of example(s) 9, wherein the user-sidepolarizer is coupled to the eyepiece at a user side of the eyepiece.

Example 15 is the method of example(s) 9, wherein the lens assembly iscoupled to the user-side polarizer.

Example 16 is the method of example(s) 9, wherein the user-sideswitchable waveplate is positioned between two layers of the lensassembly.

Example 17 is an optical system comprising: one or more world-sideshutter elements configured to: linearly polarize light associated witha world object along a first axis; and rotate a polarization of thelight associated with the world object by 90 degrees when the opticalsystem is operating in accordance with a first state; an eyepiececoupled to the one or more world-side shutter elements; a projectorconfigured to project light associated with a virtual image onto theeyepiece when the optical system is operating in accordance with asecond state; and one or more user-side shutter elements coupled to theeyepiece and configured to: linearly polarize the light associated withthe world object along a second axis perpendicular to the first axiswhen the optical system is operating in accordance with the first state;linearly polarize the light associated with the world object and thelight associated with the virtual image along the second axis when theoptical system is operating in accordance with the second state; androtate a polarization of the light associated with the virtual image by90 degrees when the optical system is operating in accordance with thesecond state.

Example 18 is the optical system of example(s) 17, further comprising: alens assembly coupled to the one or more user-side shutter elements.

Example 19 is the optical system of example(s) 18, wherein the lensassembly is configured to apply zero net optical power to the lightassociated with the world object when the optical system is operating inaccordance with the first state.

Example 20 is the optical system of example(s) 18, wherein the lensassembly is configured to apply non-zero net optical power to the lightassociated with the virtual image when the optical system is operatingin accordance with the second state.

Example 21 is the optical system of example(s) 17, wherein the eyepieceis configured to outcouple the light associated with the virtual imagetoward the one or more user-side shutter elements when the opticalsystem is operating in accordance with the second state.

Example 22 is the optical system of example(s) 17, wherein the one ormore world-side shutter elements includes: a world-side polarizer; and aworld-side switchable waveplate.

Example 23 is the optical system of example(s) 22, wherein the one ormore user-side shutter elements includes: a user-side polarizer; and auser-side switchable waveplate.

Example 24 is the optical system of example(s) 23, wherein the opticalsystem is operating in accordance with the first state when theworld-side switchable waveplate is electrically activated and theuser-side switchable waveplate is not electrically activated.

Example 25 is the optical system of example(s) 23, wherein the opticalsystem is operating in accordance with the second state when theuser-side switchable waveplate is electrically activated and theworld-side switchable waveplate is not electrically activated.

Example 26 is the optical system of example(s) 23, wherein theworld-side polarizer is coupled to the world-side switchable waveplate.

Example 27 is the optical system of example(s) 23, wherein theworld-side switchable waveplate is coupled to the eyepiece at a worldside of the eyepiece.

Example 28 is the optical system of example(s) 23, wherein the user-sidepolarizer is coupled to the eyepiece at a user side of the eyepiece.

Example 29 is the optical system of example(s) 23, wherein the lensassembly is coupled to the user-side polarizer.

Example 30 is the optical system of example(s) 23, wherein the user-sideswitchable waveplate is positioned between two layers of the lensassembly.

Example 31 is a display device comprising: a waveguide assemblyconfigured to guide light in a lateral direction parallel to an outputsurface of the waveguide assembly, the waveguide assembly furtherconfigured to outcouple the guided light through the output surface; andan adaptive lens assembly disposed on a first side of the waveguideassembly, the adaptive lens assembly disposed to receive outcoupledlight from the waveguide assembly and to be selectively switched betweena plurality of states having different optical powers, wherein theadaptive lens assembly comprises a lens stack configured to exertpolarization-dependent optical power to linearly polarized light, thelens stack comprising a birefringent lens and an isotropic lenscontacting each other, wherein contacting surfaces of the birefringentlens and the isotropic lens form a conformal interface.

Example 32 is the display device of example(s) 31, further comprising: asecond adaptive lens assembly disposed on a second side of the waveguideassembly opposite the first side, the second adaptive lens assemblyconfigured to be selectively switched between a plurality of stateshaving different optical powers and comprising: a second lens stackconfigured to exert polarization-dependent optical power to linearlypolarized light, wherein the second lens stack comprises a secondbirefringent lens and a second isotropic lens contacting each other toform a conformal interface therebetween.

Example 33 is the display device of example(s) 32, wherein each of thefirst and second adaptive lens assemblies further comprises a switchablehalf waveplate comprising twisted nematic (TN) liquid crystals (LCs)optically coupled to a respective one of the lens stack or the secondlens stack, wherein the switchable half waveplate is configured topreserve a polarization of linear polarized light passing therethroughwhen deactivated and to alter the polarization of linear polarized lightpassing therethrough when activated.

Example 34 is the display device of example(s) 33, further comprising ona second side opposite the first side of the waveguide assembly: ashutter configured to temporally alternatingly block and pass lightindent thereon; and a linear polarizer.

Example 35 is the display device of example(s) 34, wherein the waveguideassembly comprises cholesteric liquid crystals and configured tooutcouple circularly polarized light.

Example 36 is the display device of example(s) 35, wherein the waveguideassembly is interposed by a pair of quarter waveplates.

Example 37 is an optical system comprising: a projector configured toemit light; at least one waveguide optically coupled to the projectorand configured to receive and redirect light therefrom toward a user; ashutter assembly comprising at least one component positioned adjacentto the at least one waveguide, wherein the shutter assembly iscontrollable to allow a variable amount of ambient light from anenvironment of the user to pass therethrough toward the user; anadaptive lens assembly positioned between the at least one waveguide andthe user, wherein the adaptive lens assembly is controllable to impart avariable amount of optical power to light passing therethrough towardthe user; and control circuitry communicatively coupled to theprojector, the shutter assembly, and the adaptive lens assembly, whereinthe control circuitry is configured to cause the shutter assembly andthe adaptive lens assembly to synchronously switch between two or morestates comprising: a first state in which the shutter assembly isconfigured to allow a first amount of ambient light from the environmentof the user to pass therethrough toward the user and the adaptive lensassembly is configured to impart a first amount of optical power tolight passing therethrough; and a second state in which the shutterassembly is configured to allow a second amount of ambient light fromthe environment of the user to pass therethrough toward the user and theadaptive lens assembly is configured to impart a second amount ofoptical power to light passing therethrough, wherein the second amountof ambient light is less than the first amount of ambient light and thesecond amount of optical power is greater than the first amount ofoptical power.

Example 38 is the optical system of example(s) 37, wherein the firstamount of ambient light comprises a maximum amount of ambient light fromthe environment of the user to which the shutter assembly is configuredto allow to pass therethrough toward the user and the first amount ofoptical power comprises a minimum amount of optical power to which theadaptive lens assembly is configured to impart to light passingtherethrough.

Example 39 is the optical system of any of example(s)s 37 or 38,wherein, in the second state, the control circuitry is configured tocause the projector to emit light representing virtual content that isto be perceived by the user as being positioned at a first depth infront of the user.

Example 40 is the optical system of example(s) 39, wherein the controlcircuitry is configured to determine the second amount of ambient lightand the second amount of optical power based on the first depth in frontof the user at which virtual content is to be perceived by the user.

Example 41 is the optical system of example(s) 39, wherein, in the firststate, the control circuitry is configured to cause the projector toemit light representing virtual content that is to be perceived by theuser as being positioned at a second depth in front of the user, thesecond depth being greater than the first depth.

Example 42 is the optical system of example(s) 41, wherein the seconddepth is substantially equivalent to optical infinity.

Example 43 is the optical system of example(s) 39, wherein, in the firststate, the control circuitry is configured to cause the projector to notemit light.

Example 44 is the optical system of any of example(s)s 37 or 38, whereinthe control circuitry is configured to cause the shutter assembly andthe adaptive lens assembly to synchronously switch between the two ormore states at a rate greater than or equal to a minimum switchingfrequency.

Example 45 is the optical system of example(s) 44, wherein the minimumswitching frequency is 120 Hz.

Example 46 is the optical system of example(s) 44, further comprising:an ambient light sensor configured to measure an intensity of ambientlight from the environment of the user; wherein the control circuitry iscommunicatively coupled to the ambient light sensor and furtherconfigured to determine the rate at which to cause the shutter assemblyand the adaptive lens assembly to synchronously switch between the twoor more states based on data received from the ambient light sensor.

Example 47 is the optical system of example(s) 38, wherein the minimumamount of optical power to which the adaptive lens assembly isconfigured to impart to light passing therethrough is about zero.

Example 48 is the optical system of any of the above examples, whereinthe second amount of ambient light comprises a minimum amount of ambientlight from the environment of the user to which the shutter assembly isconfigured to allow to pass therethrough toward the user and the secondamount of optical power comprises a maximum amount of optical power towhich the adaptive lens assembly is configured to impart to lightpassing therethrough.

Example 49 is an optical system comprising: a projector configured toemit light; at least one waveguide optically coupled to the projectorand configured to receive and redirect light therefrom toward a user; ashutter assembly comprising at least one component positioned adjacentto the at least one waveguide, wherein the shutter assembly iscontrollable to allow a variable amount of ambient light from anenvironment of the user to pass therethrough toward the user; anadaptive lens assembly positioned between the at least one waveguide andthe user, wherein the adaptive lens assembly is controllable to impart avariable amount of optical power to light passing therethrough towardthe user; and control circuitry communicatively coupled to theprojector, the shutter assembly, and the adaptive lens assembly, whereinthe control circuitry is configured to synchronously: cause the adaptivelens assembly to vary the amount of optical power imparted to lightpassing therethrough toward the user; and cause the shutter assembly tovary the amount of ambient light from the environment of the userallowed to pass therethrough toward the user inversely with the amountof optical power imparted by the adaptive lens assembly to light passingtherethrough.

Example 50 is the optical system of any of the above examples, whereinthe at least one waveguide is further configured to allow ambient lightfrom the environment of the user to pass therethrough toward the user.

Example 51 is the optical system of any of the examples above, whereinthe at least one component of the shutter assembly comprises at leastone component positioned between the at least one waveguide and theenvironment of the user.

Example 52 is the optical system of any of the examples above, whereinthe at least one component of the shutter assembly comprises at leastone component positioned between the at least one waveguide and theuser.

Example 53 is the optical system of any of the examples above, whereinthe at least one component of the shutter assembly comprises at leastone component positioned between the at least one waveguide and theadaptive lens assembly.

Example 54 is the optical system of any of the above examples, whereinthe at least one waveguide comprises a plurality of waveguides.

Example 55 is a non-transitory computer-readable medium storinginstructions that, when executed by one or more processors, cause theone or more processors to at least in part perform the methods of any ofthe above examples.

Example 56 is an optical system comprising: a projector configured toemit light; at least one waveguide optically coupled to the projectorand configured to receive and redirect light therefrom toward a user; ashutter assembly comprising at least one component positioned adjacentto the at least one waveguide, wherein the shutter assembly isselectively switchable between different states in which the shutterassembly is configured to allow different amounts of ambient light froman environment of the user to pass therethrough toward the user,respectively; an adaptive lens assembly positioned between the at leastone waveguide and the user, wherein the adaptive lens assembly isselectively switchable between different states in which the adaptivelens is configured to impart different amounts of wavefront divergenceto light passing therethrough toward the user, respectively; and controlcircuitry communicatively coupled to the projector, the shutterassembly, and the adaptive lens assembly.

Example 57 is the optical system of example 56, wherein the controlcircuitry is configured to cause the shutter assembly and the adaptivelens assembly to synchronously switch between two or more states at aparticular rate, the two or more states comprising: a first state inwhich the shutter assembly is configured to allow a first amount ofambient light from the environment of the user to pass therethroughtoward the user and the adaptive lens assembly is configured to impart afirst amount of wavefront divergence to light passing therethrough; anda second state in which the shutter assembly is configured to allow asecond amount of ambient light from the environment of the user to passtherethrough toward the user and the adaptive lens assembly isconfigured to impart a second amount of wavefront divergence to lightpassing therethrough, wherein the second amount of ambient light isdifferent from the first amount of ambient light and the second amountof wavefront divergence is different from the first amount of wavefrontdivergence.

Example 58 is the optical system of example 57, wherein the particularrate at which to cause the shutter assembly and the adaptive lensassembly to synchronously switch between the two or more statescomprises a rate greater than or equal to a minimum switching frequency.

Example 59 is the optical system of examples 57 or 58 further comprisingan ambient light sensor configured to measure an intensity of ambientlight from the environment of the user, wherein the control circuitry iscommunicatively coupled to the ambient light sensor and furtherconfigured to determine the particular rate at which to cause theshutter assembly and the adaptive lens assembly to synchronously switchbetween the two or more states based on data received from the ambientlight sensor.

Example 60 is the optical system of examples 58 or 59, wherein theminimum switching frequency is 120 Hz.

Example 61 is the optical system of example 57, wherein the first amountof ambient light comprises a maximum amount of ambient light from theenvironment of the user to which the shutter assembly is configured toallow to pass therethrough toward the user and the first amount ofwavefront divergence comprises a minimum amount of wavefront divergenceto which the adaptive lens assembly is configured to impart to lightpassing therethrough.

Example 62 is the optical system of any of examples 57 or 61, wherein,in the second state, the control circuitry is configured to cause theprojector to emit light representing virtual content that is to beperceived by the user as being positioned at a first depth in front ofthe user.

Example 63 is the optical system of example 62, wherein the controlcircuitry is configured to determine at least one of the second amountof ambient light and the second amount of wavefront divergence based onthe first depth in front of the user at which virtual content is to beperceived by the user.

Example 64 is the optical system of example 62, wherein, in the firststate, the control circuitry is configured to cause the projector toemit light representing virtual content that is to be perceived by theuser as being positioned at a second depth in front of the user, thesecond depth being greater than the first depth.

Example 65 is the optical system of example 64, wherein the second depthis substantially equivalent to optical infinity.

Example 66 is the optical system of example 62, wherein, in the firststate, the control circuitry is configured to cause the projector to notemit light.

Example 67 is the optical system of example 61, wherein the minimumamount of wavefront divergence to which the adaptive lens assembly isconfigured to impart to light passing therethrough is about zero.

Example 68 is the optical system of claim 57, wherein the second amountof ambient light is less than the first amount of ambient light and thesecond amount of wavefront divergence is greater than the first amountof wavefront divergence.

Example 69 is the optical system of any of the above examples, whereinthe second amount of ambient light comprises a minimum amount of ambientlight from the environment of the user to which the shutter assembly isconfigured to allow to pass therethrough toward the user and the secondamount of wavefront divergence comprises a maximum amount of wavefrontdivergence to which the adaptive lens assembly is configured to impartto light passing therethrough.

Example 70 is the optical system of example 56, wherein the controlcircuitry is configured to cause the shutter assembly and the adaptivelens assembly to synchronously switch between different states in amanner yielding an inverse relationship between the amount of ambientlight from the environment of the user allowed by the shutter assemblyto pass therethrough toward the user and the amount of wavefrontdivergence imparted by the adaptive lens assembly to light passingtherethrough toward the user.

Example 71 is the optical system of example 56, wherein the controlcircuitry is configured to alternate between at least two differentmodes of operation comprising: a first mode of operation in which thecontrol circuitry is configured to control a state of the shutterassembly and a state of the adaptive lens assembly in an asynchronousmanner; and a second mode of operation in which the control circuitry isconfigured to control the state of the shutter assembly and the state ofthe adaptive lens assembly in a synchronous manner.

Example 72 is the optical system of example 71, wherein, in the secondmode of operation, the control circuitry is configured to cause theshutter assembly and the adaptive lens assembly to synchronously switchbetween two or more states comprising: a first state in which theshutter assembly is configured to allow a first amount of ambient lightfrom the environment of the user to pass therethrough toward the userand the adaptive lens assembly is configured to impart a first amount ofwavefront divergence to light passing therethrough; and a second statein which the shutter assembly is configured to allow a second amount ofambient light from the environment of the user to pass therethroughtoward the user and the adaptive lens assembly is configured to impart asecond amount of wavefront divergence to light passing therethrough,wherein the second amount of ambient light is different from the firstamount of ambient light and the second amount of wavefront divergence isdifferent from the first amount of wavefront divergence.

Example 73 is the optical system of example 71 further comprising one ormore cameras configured to capture images of one or both of the user'seyes, wherein the control circuitry is communicatively coupled to theone or more cameras and further configured to alternate between the atleast two different modes of operation based at least in part on datareceived from the one or more cameras.

Example 74 is the optical system of example 73, wherein the controlcircuitry is further configured to: determine a depth at which theuser's eyes are fixated based on data received from the one or morecameras; and alternate between the at least two different modes ofoperation based at least in part on the depth at which the user's eyesare determined to be fixated.

Example 75 is the optical system of example 71, wherein the controlcircuitry is further configured to cause the projector to emit lightrepresenting virtual content.

Example 76 is the optical system of example 75, wherein the controlcircuitry is further configured to: determine whether anaccommodation-vergence mismatch for the virtual content exceeds athreshold; and alternate between the at least two different modes ofoperation in response to a determination that the accommodation-vergencemismatch for the virtual content exceeds the threshold.

Example 77 is the optical system of example 75, wherein the controlcircuitry is further configured to alternate between the at least twodifferent modes of operation based at least in part on a depth in frontof the user at which the virtual content is to be perceived by the user.

Example 78 is the optical system of example 71, wherein, in the firstmode of operation, the control circuitry is configured to cause thestate of at least one of the shutter assembly and the adaptive lensassembly to remain substantially fixed.

Example 79 is the optical system of any of the above examples, whereinthe at least one waveguide is further configured to allow ambient lightfrom the environment of the user to pass therethrough toward the user.

Example 80 is the optical system of any of the above examples, whereinthe at least one component of the shutter assembly comprises at leastone component positioned between the at least one waveguide and theenvironment of the user.

Example 81 is the optical system of any of the above examples, whereinthe at least one component of the shutter assembly comprises at leastone component positioned between the at least one waveguide and theuser.

Example 82 is the optical system of any of the above examples, whereinthe at least one component of the shutter assembly comprises at leastone component positioned between the at least one waveguide and theadaptive lens assembly.

Example 83 is the optical system of any of the above examples, whereinthe at least one waveguide comprises a plurality of waveguides.

Example 84 is an optical system comprising: a projector configured toemit light; at least one waveguide optically coupled to the projectorand configured to receive and redirect light therefrom toward a user; ashutter assembly comprising at least one component positioned adjacentto the at least one waveguide, wherein the shutter assembly isselectively switchable between different states in which the shutterassembly is configured to allow different amounts of ambient light froman environment of the user to pass therethrough toward the user,respectively; an adaptive lens assembly positioned between the at leastone waveguide and the user, wherein the adaptive lens assembly isselectively switchable between different states in which the adaptivelens is configured to impart different amounts of wavefront divergenceto light passing therethrough toward the user, respectively; and controlcircuitry communicatively coupled to the projector, the shutterassembly, and the adaptive lens assembly, wherein the control circuitryis configured to cause the shutter assembly and the adaptive lensassembly to synchronously switch between two or more states at aparticular rate, the two or more states comprising: a first state inwhich the shutter assembly is configured to allow a first amount ofambient light from the environment of the user to pass therethroughtoward the user and the adaptive lens assembly is configured to impart afirst amount of wavefront divergence to light passing therethrough; anda second state in which the shutter assembly is configured to allow asecond amount of ambient light from the environment of the user to passtherethrough toward the user and the adaptive lens assembly isconfigured to impart a second amount of wavefront divergence to lightpassing therethrough, wherein the second amount of ambient light isdifferent from the first amount of ambient light and the second amountof wavefront divergence is different from the first amount of wavefrontdivergence.

Example 85 is the optical system of example 84, wherein the secondamount of ambient light is less than the first amount of ambient lightand the second amount of wavefront divergence is greater than the firstamount of wavefront divergence.

Example 86 is the optical system of example 84, wherein the particularrate at which to cause the shutter assembly and the adaptive lensassembly to synchronously switch between the two or more statescomprises a rate greater than or equal to a minimum switching frequency.

Example 87 is the optical system of example 84, wherein in the secondstate, the control circuitry is configured to cause the projector toemit light representing virtual content that is to be perceived by theuser as being positioned at a first depth in front of the user; andwherein the control circuitry is configured to determine at least one ofthe second amount of ambient light and the second amount of wavefrontdivergence based on the first depth in front of the user at whichvirtual content is to be perceived by the user.

Example 88 is the optical system of example 84, wherein the at least onecomponent of the shutter assembly comprises at least one componentpositioned between the at least one waveguide and the user.

Example 89 is an optical system comprising: a projector configured toemit light; at least one waveguide optically coupled to the projectorand configured to receive and redirect light therefrom toward a user; ashutter assembly comprising at least one component positioned adjacentto the at least one waveguide, wherein the shutter assembly iscontrollable to allow a variable amount of ambient light from anenvironment of the user to pass therethrough toward the user; anadaptive lens assembly positioned between the at least one waveguide andthe user, wherein the adaptive lens assembly is controllable to impart avariable amount of wavefront divergence to light passing therethroughtoward the user; and control circuitry communicatively coupled to theprojector, the shutter assembly, and the adaptive lens assembly, whereinthe control circuitry is configured to synchronously: cause the adaptivelens assembly to vary the amount of wavefront divergence imparted tolight passing therethrough toward the user; and cause the shutterassembly to vary the amount of ambient light from the environment of theuser allowed to pass therethrough toward the user inversely with theamount of wavefront divergence imparted by the adaptive lens assembly tolight passing therethrough.

Example 90 is an optical system comprising: a projector configured toemit light; at least one waveguide optically coupled to the projectorand configured to receive and redirect light therefrom toward a user; ashutter assembly comprising at least one component positioned adjacentto the at least one waveguide, wherein the shutter assembly isselectively switchable between different states in which the shutterassembly is configured to allow different amounts of ambient light froman environment of the user to pass therethrough toward the user,respectively; an adaptive lens assembly positioned between the at leastone waveguide and the user, wherein the adaptive lens assembly isselectively switchable between different states in which the adaptivelens is configured to impart different amounts of wavefront divergenceto light passing therethrough toward the user, respectively; and controlcircuitry communicatively coupled to the projector, the shutterassembly, and the adaptive lens assembly, wherein the control circuitryis configured to cause the shutter assembly and the adaptive lensassembly to synchronously switch between different states in a manneryielding an inverse relationship between the amount of ambient lightfrom the environment of the user allowed by the shutter assembly to passtherethrough toward the user and the amount of wavefront divergenceimparted by the adaptive lens assembly to light passing therethroughtoward the user.

Example 91 is an optical system comprising: a projector configured toemit light; at least one waveguide optically coupled to the projectorand configured to receive and redirect light therefrom toward a user; ashutter assembly comprising at least one component positioned adjacentto the at least one waveguide, wherein the shutter assembly isselectively switchable between different states in which the shutterassembly is configured to allow different amounts of ambient light froman environment of the user to pass therethrough toward the user,respectively; an adaptive lens assembly positioned between the at leastone waveguide and the user, wherein the adaptive lens assembly isselectively switchable between different states in which the adaptivelens is configured to impart different amounts of wavefront divergenceto light passing therethrough toward the user, respectively; and controlcircuitry communicatively coupled to the projector, the shutterassembly, and the adaptive lens assembly, wherein the control circuitryis configured to alternate between at least two different modes ofoperation comprising: a first mode of operation in which the controlcircuitry is configured to control a state of the shutter assembly and astate of the adaptive lens assembly in an asynchronous manner; and asecond mode of operation in which the control circuitry is configured tocontrol the state of the shutter assembly and the state of the adaptivelens assembly in a synchronous manner.

Example 92 is a non-transitory computer-readable medium storinginstructions that, when executed by one or more processors, cause theone or more processors to perform one or more of the operationsperformed by the control circuitry of any of the above examples.

Numerous benefits are achieved by way of the present disclosure overconventional techniques. Various embodiments described herein provide acompact, time-multiplexed display that can apply optical power tovirtual image light so as to provide virtual content at various depthswhile at the same time leaving world light undistorted. Variousembodiments described herein also provide adaptive lens assemblies thatinclude a polarization-selective lens stack. In certain implementations,the polarization-selective lens stack comprises a birefringent lens,e.g., a Fresnel birefringent lens, and an isotropic lens contacting eachother. Such assemblies can be compact (e.g., can have reduced thickness)and/or lightweight. These assemblies may potentially also providevarious advantageous optical functionalities such as high bandwidth,increased switching speeds, reduced chromatic aberrations, increasedease of alignment, and/or variable optical power. Some embodiments ofthe disclosure provide for replacing the conventional front adaptivelens assembly with a shutter assembly, yielding smaller/lighter formfactors and increased power savings. In addition, various embodimentsdescribed herein can provide adaptive lens assemblies with relativelylow amount of leakage light that can otherwise lead to “ghost” images.Other benefits of the present disclosure will be readily apparent tothose skilled in the art.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates an augmented reality (AR) scene as viewed through awearable AR device according to an embodiment described herein.

FIG. 2 illustrates an example of a display system comprising a pair ofadaptive lens assemblies.

FIG. 3A illustrates an example of the display system of FIG. 2displaying virtual content to a user at a virtual depth plane using anadaptive lens.

FIG. 3B illustrates an example of the display system of FIG. 2 providinga view of real world content to a user through adaptive lenses.

FIGS. 4A-4C illustrate one or more general features of an AR deviceaccording to the present disclosure.

FIG. 5 illustrates a schematic view of a wearable AR device according tothe present disclosure.

FIG. 6A illustrates a cross-sectional view of an examplepolarization-selective lens stack comprising a birefringent lens and anisotropic lens.

FIG. 6B illustrates the polarization-selective lens stack of FIG. 6A inoperation, passing therethrough linearly polarized light having a firstpolarization.

FIG. 6C illustrates the polarization-selective lens stack of FIG. 6A inoperation, passing therethrough linearly polarized light having a secondpolarization.

FIG. 7A illustrates the polarization-selective lens stack of FIG. 6Awith annotated parameters.

FIG. 7B illustrates cross-sectional and top down views of an example ofa polarization-selective lens stack comprising a birefringent Fresnellens and an isotropic lens.

FIG. 8A illustrates a cross-sectional view of an example adaptive lensassembly comprising a polarization-selective lens stack coupled with aswitchable waveplate comprising twisted nematic liquid crystals.

FIG. 8B illustrates the switchable waveplate comprising twisted nematicliquid crystals of adaptive lens assembly illustrated in FIG. 8A.

FIG. 9A illustrates a cross-sectional view of an example adaptive lensassembly comprising a first polarization-selective lens stack coupledwith a first switchable waveplate comprising twisted nematic liquidcrystals and a second polarization-selective lens stack coupled with asecond switchable waveplate comprising twisted nematic liquid crystals.

FIGS. 9B-9E illustrate the example adaptive lens assembly of FIG. 9A inoperation under different configurations configured to exert differentoptical powers.

FIG. 10 illustrates a cross-sectional view of an example display devicecomprising a waveguide assembly interposed between a first adaptive lensassembly and a second adaptive assembly each having apolarization-selective lens stack.

FIG. 11A illustrates a cross-sectional view of an example display devicecomprising a waveguide assembly interposed between a shutter and alinear polarizer on a first side and an adaptive assembly having apolarization-selective lens stack on a second side.

FIG. 11B illustrates the waveguide assembly of the display device ofFIG. 11A, comprising cholesteric liquid crystals and configured tooutcouple circularly polarized light.

FIG. 11C illustrates the example display device of FIG. 11A inoperation, under configuration for viewing world images.

FIG. 11D illustrates the example display device of FIG. 11A inoperation, under configuration for viewing virtual images.

FIG. 12A illustrates an example of a display device having a singleadaptive lens assembly on the user side of an eyepiece, according tosome embodiments of the present disclosure.

FIG. 12B illustrates an example of a display device operating inaccordance with a first state, according to some embodiments of thepresent disclosure.

FIG. 12C illustrates an example of a display device operating inaccordance with a second state, according to some embodiments of thepresent disclosure.

FIG. 13 illustrates a method of operating an optical system, accordingto some embodiments of the present disclosure.

FIG. 14 illustrates a method of operating an optical system, accordingto some embodiments of the present disclosure.

FIG. 15 illustrates an example performance of a method of operating anoptical system, according to some embodiments of the present disclosure.

FIG. 16A illustrates an example of a display device operating inaccordance with a first state, according to some embodiments of thepresent disclosure.

FIG. 16B illustrates an example of a display device operating inaccordance with a second state, according to some embodiments of thepresent disclosure.

FIG. 16C illustrates an example of a display device operating inaccordance with a third state, according to some embodiments of thepresent disclosure.

FIG. 17 illustrates a simplified computer system according to anembodiment described herein.

DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS

Optical see through (OST) augmented reality (AR) devices can improve thevirtual content being presented to a user by applying optical power tothe virtual image light (i.e., light associated with a virtual image)using one or more adaptive lens assemblies arranged within the opticalstack. One issue with such configurations is that optical power isnecessarily also applied to the world light (i.e., light associated witha world object) passing therein, causing distortion of the perceivedworld object and thereby diminishing the user experience. Someembodiments described herein overcome these and other issues byproviding various shutter elements arranged within the optical stackthat may be sequentially activated to produce the result of world lightbeing passed through the AR device without distortion and virtual imagelight being imparted optical power from the adaptive lens assembly asneeded.

FIG. 1 illustrates an AR scene as viewed through a wearable AR deviceaccording to an embodiment described herein. An AR scene 100 is depictedwherein a user of an AR technology sees a real-world park-like setting106 featuring people, trees, buildings in the background, and a concreteplatform 120. In addition to these items, the user of the AR technologyalso perceives that he “sees” a robot statue 110 standing upon thereal-world platform 120, and a cartoon-like avatar character 102 flyingby, which seems to be a personification of a bumble bee, even thoughthese elements (character 102 and statue 110) do not exist in the realworld. Due to the extreme complexity of the human visual perception andnervous system, it is challenging to produce a virtual reality (VR) orAR technology that facilitates a comfortable, natural-feeling, richpresentation of virtual image elements amongst other virtual orreal-world imagery elements.

FIG. 2 illustrates an example of a display device 200, e.g., a wearabledisplay device, comprising one or more adaptive lens assembliesincluding a polarization-selective lens stack, e.g., a pair of adaptivelens assemblies 204, 208 in an optical path 216 that are interposed by awaveguide assembly 212. As described herein, waveguide assembly 212 mayinclude a waveguide configured to propagate light (e.g., visible light)under total internal reflection and to outcouple the light in an opticalaxis extending from (e.g., in a direction normal to) a light outputsurface of the waveguide (e.g., a major surface of the waveguide). Thelight may be outcoupled by a diffraction grating in some embodiments.Each of adaptive lens assemblies 204, 208 may be configured to at leastpartially transmit outcoupled light therethrough. In the illustratedembodiments, each of adaptive lens assemblies 204, 208 may be configuredto receive outcoupled light from waveguide assembly 212 and to convergeor diverge the outcoupled light in the optical axis direction. Each ofadaptive lens assemblies 204, 208 comprises a polarization-selectivelens stack comprising a birefringent lens and an isotropic lenscontacting each other, wherein contacting surfaces of the birefringentlens and the isotropic lens form a conformal interface therebetween.Each of adaptive lens assemblies 204, 208 is configured to beselectively switched between a plurality of states having differentoptical powers. That is, each of adaptive lens assemblies 204, 208 isconfigured to be selectively switched between a plurality of states inwhich the respective adaptive lens assembly is configured to impartdifferent amounts of wavefront divergence or convergence to lightpassing therethrough. Each of adaptive lens assemblies 204, 208 canfurther be configured to alter a polarization state of the outcoupledlight passing therethrough when activated (e.g., electricallyactivated).

As used herein, an adaptive lens assembly refers to a lens assemblyhaving at least one optical property that may be adjusted, e.g.,reversibly activated and deactivated, using an external stimulus.Example optical properties that may be reversibly activated anddeactivated include, among other properties, optical power (focallength), phase, polarization, polarization-selectivity, transmissivity,reflectivity, birefringence and diffraction properties, among otherproperties. In various embodiments, adaptive lens assemblies are capableof electrically varying the optical power and the polarization state oflight passing therethrough.

In the illustrated embodiment, each of the pair of adaptive lensassemblies 204, 208 is configured to be selectively switched between atleast two states, where, in a first state each is configured to pass theoutcoupled light therethrough without altering a polarization statethereof, while in a second state each is configured to alter thepolarization state of the outcoupled light passing therethrough. Forexample, in the second state, each of adaptive lens assemblies 204, 208reverses the handedness of circularly polarized light, while in thefirst state, each of adaptive lens assemblies 204, 208 preserves thehandedness of circularly polarized light.

Still referring to FIG. 2, display device 200 may further comprisewaveguide assembly 212 interposed between the pair of adaptive lensassemblies 204, 208. Each of waveguide assemblies 204, 208 may beconfigured to propagate light under total internal reflection in alateral direction parallel to a major surface of the waveguide. Each ofwaveguide assemblies 204, 208 may further be configured to outcouple thelight, e.g., in a direction normal to the major surface of thewaveguide.

Still referring to FIG. 2, a first adaptive lens assembly 204 of thepair of adaptive lens assemblies is disposed on a first side ofwaveguide assembly 212, e.g., the side of the world observed by a user,and a second adaptive lens assembly 208 of the pair of lens assembliesis disposed on a second side of the waveguide assembly 212, e.g., theside of the eye of the user. As described infra, the pair of adaptivelens assemblies 204, 208 as configured provides to a user virtualcontent from waveguide assembly 212 at a plurality of virtual depthplanes, as well the view of the real world. In some embodiments, thereis little or no distortion due to the presence of the pair of adaptivelens assemblies 204, 208. The virtual content and the view of the realworld are provided to the user upon activation of the first and secondadaptive lens assemblies 204, 208, as described infra with respect toFIGS. 3A and 3B.

FIGS. 3A and 3B illustrate examples of display devices 300A, 300B, eachcomprising adaptive lens assemblies in operation to output imageinformation to a user. Display devices 300A, 300B may correspond to thesame display device at different times and/or in different states. Insome embodiments, display devices 300A, 300B in unpowered states arestructurally identical. Display device 300A is used herein to describeoutputting virtual image to the user, while display device 300B is usedherein to describe transmitting a real world image through the displaydevice 300B to the user. Display devices 300A, 300B include a pair ofadaptive lens assemblies 204, 208 that are configured to be electricallyactivated by, e.g., application of a voltage or a current. In someembodiments, in a deactivated state, e.g., when no voltage or current isapplied, each of first and second adaptive lens assemblies 204, 208 hasa low, e.g., about zero, optical power. In some embodiments, in anactivated state, e.g., when a voltage or a current is applied, firstadaptive lens assembly 204 on the side of the world may provide a firstnet optical power (P_(net1)) having a first sign, e.g., a positiveoptical power. When in an activated state, second adaptive lens assembly208 on the side of the user may provide a second net optical power(P_(net2)) having a second sign, e.g., a negative optical power.However, embodiments are not so limited, and in other embodiments, firstand second adaptive lens assemblies 200A, 200B may provide the opticalpowers in the deactivated state while providing substantially zero powerwhen activated.

FIG. 3A illustrates an example of the display system of FIG. 2displaying virtual content to a user at a virtual depth plane 304,according to some embodiments. As described supra, waveguide assembly212 interposed between the pair of adaptive lens assemblies 204, 208comprises a waveguide configured to receive light containing virtualimage information and propagate the light under total internalreflection. Waveguide assembly 212 is further configured to outcouplethe light through, e.g., a diffraction grating, towards the eye of theuser. The outcoupled light passes through user-side adaptive lensassembly 208 prior to entering the eye of the user. When activated,user-side adaptive lens assembly 208 has a second net optical power,P_(net2), which may have a negative value, such that the user sees thevirtual image at a virtual depth plane 304.

In some embodiments, the second net optical power P_(net2) may beadjusted electrically to adjust the second net optical power (P_(net2))of user-side adaptive lens assembly 208, thereby adjusting the distanceto virtual depth plane 304. For example, as a virtual object “moves”closer and further relative to the eye of the user within a virtualthree dimensional space, the second net optical power P_(net2) ofuser-side adaptive lens assembly 208 may be correspondingly adjusted,such that virtual depth plane 304 adjusts to track the virtual object.Thus, the user may experience relatively little or noaccommodation/vergence mismatch beyond an acceptable threshold. In someembodiments, the magnitude of the distance to virtual depth plane 304may be adjusted in discrete steps, while in some other embodiments, themagnitude of the distance to virtual depth plane 304 may be adjustedcontinuously.

FIG. 3B illustrates an example of the display system of FIG. 2 providinga view of real world content to a user, according to some embodiments.When user-side adaptive lens assembly 208 is activated to have thesecond net optical power (P_(net2)) to display the virtual content atvirtual depth plane 304, light from the real world passing throughuser-side adaptive lens assembly 208 may also be converged or divergedaccording to P_(net2) of the activated user-side adaptive lens assembly208. Thus, objects in the real world may appear out of focus ordistorted. To mitigate such distortion, according to embodiments, whenactivated, adaptive lens assemblies 204, 208 may be configured to haveoptical powers having opposite signs. In some embodiments, light passingthrough adaptive lens assemblies 204, 208 converges or divergesaccording to a combined optical power having a magnitude that is about adifference between magnitudes of first and second net optical powersP_(net1), P_(net2), of world-side and user-side adaptive lens assemblies204, 208, respectively. In some embodiments, waveguide assembly 212 mayalso have optical power and adaptive lens assembly 208 may be configuredto account for the distortions caused by both lens assembly 204 andwaveguide assembly 212. For example, the optical power of adaptive lensassembly 208 may be opposite in sign to the sum of the optical powers ofadaptive lens assembly 204 and waveguide assembly 212.

In some embodiments, world-side adaptive lens assembly 204 is configuredto have the first net optical power P_(net1) that has a magnitude thatis close to or the same as the magnitude of the second net optical powerP_(net2) of user-side adaptive lens assembly 208 while having anopposite sign. As a result, when both of adaptive lens assemblies 204,208 are activated simultaneously, objects in the real world appearrelatively unaffected by the optical power of user-side adaptive lensassembly 208 provided for displaying the virtual content.

In some embodiments, first adaptive lens assembly 204 may be configuredsuch that when activated, the first net optical power P_(net1)dynamically matches the second net optical power P_(net2) of user-sideadaptive lens assembly 208. For example, as the second net optical powerP_(net2) of user-side adaptive lens assembly 208 is adjusted to trackmoving virtual objects within the virtual three dimensional space, thefirst net optical power P_(net1) of world-side adaptive lens assembly204 may be dynamically adjusted, such that the magnitude of the combinedoptical power P=P_(net1)+P_(net2) may be kept less than a predeterminedvalue. Thus, according to embodiments, the objects in the real world maybe prevented from being unacceptably out of focus by compensating thesecond net optical power (P_(net2)) of user-side adaptive lens assembly208, which may have a negative value, with the first net optical power(P_(net1)) of world-side adaptive lens assembly 204, such that thecombined optical power P=P_(net1)+P_(net2) remains small. As describedin further detail below, in some implementations, a wearable displaydevice may include a waveguide assembly and a user-side adaptive lensassembly that are functionally equivalent or similar to waveguideassembly 212 and user-side adaptive lens assembly 208, respectively, butmay not include a world-side adaptive lens assembly similar to that ofworld-side adaptive lens assembly 204. Instead, as described in furtherdetail below, in these implementations, the display device may includeone or more shutter elements, and may be configured to control such oneor more shutter elements in synchronization with the user-side adaptivelens in a manner such that objects in the real world are not renderedunacceptably out of focus by the optical power imparted by the user-sideadaptive lens.

FIG. 4A illustrates one or more general features of an AR device 400according to the present disclosure. As shown in FIG. 4A, AR device 400includes an eyepiece 402 and an adaptive lens assembly 405, which may befunctionally equivalent or similar to waveguide assembly 212 anduser-side adaptive lens assembly 208, respectively, as described above.During operation, a projector 414 of AR device 400 may project virtualimage light 423 (i.e., light associated with a virtual image) ontoeyepiece 402, which may cause a light field (i.e., an angularrepresentation of virtual content) to be projected onto the user'sretina in a manner such that the user perceives the correspondingvirtual content as being positioned at some location within the user'senvironment. For example, the user may perceive character 102 as beingpositioned at or near a first virtual depth and statue 110 as beingpositioned at or near a second virtual depth. While AR device 400 mayinclude only one adaptive lens assembly 405 (e.g., positioned on theuser side of eyepiece 402 i.e., the side of eyepiece 402 closest to theeye of the user), such an adaptive lens assembly may be capable ofimparting a plurality of different non-zero optical powers to lightpassing therethrough. That is, adaptive lens assembly 405 may be capableof imparting a plurality of different amounts of at least one ofwavefront divergence and collimation to light passing therethrough.

AR device 400 may also include one or more shutter elements 403 coupledto the world side of eyepiece 402 (the side of eyepiece 402 furthestfrom the eye of the user and closest to world objects 430) and/or to theuser side of eyepiece 402. By sequentially electrically activatingdifferent elements/layers of shutter elements 403 as described herein,world light 432 associated with world objects 430 may pass through ARdevice 400 with zero net optical power being applied by lens assembly405 and virtual image light 423 may pass through with non-zero (e.g.,negative) net optical power being applied by lens assembly 405. Exampledimming components, which may represent or be included in shutterelements 403 and other shutter assemblies described herein, aredescribed in U.S. Patent Application Publication No. 2020/0074724, filedAug. 30, 2019, and International Patent Application No.PCT/US2019/051188, filed on Sep. 13, 2019, all of which are incorporatedby reference herein in their entirety.

In some embodiments, AR device 400 may include an ambient light sensor434 configured to detect world light 432. Ambient light sensor 434 maybe positioned such that world light 432 detected by ambient light sensor434 is similar to and/or representative of world light 432 that impingeson AR device 400 (e.g., shutter elements 403, eyepiece 402 and/or lensassembly 405). In some embodiments, ambient light sensor 434 may beconfigured to detect a plurality of spatially-resolved light valuescorresponding to different pixels of the field of view of AR device 400.In some embodiments, or in the same embodiments, ambient light sensor434 may be configured to detect a global light value corresponding to anaverage light intensity or a single light intensity of world light 432.Detected ambient light may be used by AR device 400 to determine ashuttering frequency at which AR device 400 alternates between operatingin accordance with a first state or a second state. In some instances,the shuttering frequency may exceed the flicker fusion threshold, suchthat the shuttering may not be readily perceivable to the user. Forexample, the shuttering frequency may be at least 120 Hz (e.g., 160 Hzor 200 Hz).

FIG. 4B illustrates AR device 400 operating in accordance with a firststate, according to some embodiments of the present disclosure. Whileoperating in accordance with the first state, projector 414 is turnedoff and one or more of shutter elements 403 are electrically activatedsuch that world light 432 passes through AR device 400 with zero netoptical power being applied by lens assembly 405. As will be shownbelow, this is accomplished using a world-side polarizer of shutterelements 403 to linearly polarize world light 432 along a first axis, aworld-side switchable waveplate of shutter elements 403 to rotate apolarization of world light 432 by 90 degrees, and a user-side polarizerof shutter elements 403 to linearly polarize world light 432 along asecond axis perpendicular to the first axis.

In some embodiments, one or more components of shutter elements 403 areconsidered to be subcomponents of lens assembly 405 (i.e., areconsidered to be included in lens assembly 405). For example, theuser-side polarizer of shutter elements 403 may be considered to be asubcomponent of lens assembly 405. In such embodiments, when AR device400 is operating in accordance with the first state, lens assembly 405is considered to be switched, activated, and/or controlled into a statein which it applies zero optical power to light passing therethrough.

FIG. 4C illustrates AR device 400 operating in accordance with a secondstate, according to some embodiments of the present disclosure. Whileoperating in accordance with the second state, projector 414 is turnedon and one or more of shutter elements 403 are electrically activatedsuch that world light 432 is completely or at least partially reduced,blocked, or dimmed, and virtual image light 423 passes through AR device400 with non-zero net optical power being applied by lens assembly 405.As will be shown below, this is accomplished using a world-sidepolarizer of shutter elements 403 to linearly polarize world light 432along a first axis, a user-side polarizer of shutter elements 403 tolinearly polarize world light 432 and virtual image light 423 along asecond axis perpendicular to the first axis, and a user-side switchablewaveplate of shutter elements 403 to rotate a polarization of virtualimage light 423 by 90 degrees.

Similar to that described in reference to FIG. 4B, in some embodiments,one or more components of shutter elements 403 are considered to besubcomponents of lens assembly 405 (i.e., are considered to be includedin lens assembly 405). For example, the user-side polarizer of shutterelements 403 may be considered to be a subcomponent of lens assembly405. In such embodiments, when AR device 400 is operating in accordancewith the second state, lens assembly 405 is considered to be switched,activated, and/or controlled into a state in which it applies non-zerooptical power to light passing therethrough. In some examples, (e.g.,those described in reference to FIGS. 11C and 11D), a polarizingeyepiece may also be switched, activated, and/or controlled with eachstate such that the optical power applied to the light it outcouples mayvary.

FIG. 5 illustrates a schematic view of a wearable AR device 500according to the present disclosure. AR device 500 may include a lefteyepiece 502A, left shutter elements 503A, and a left lens assembly 505Aarranged in a side-by-side configuration and a right eyepiece 502B,right shutter elements 503B, and a right lens assembly 505B alsoarranged in a side-by-side configuration. In some embodiments, AR device500 includes one or more sensors including, but not limited to: a leftfront-facing world camera 506A attached directly to or near lefteyepiece 502A, a right front-facing world camera 506B attached directlyto or near right eyepiece 502B, a left side-facing world camera 506Cattached directly to or near left eyepiece 502A, a right side-facingworld camera 506D attached directly to or near right eyepiece 502B, aleft eye tracker positioned so as to observe a left eye of a user, aright eye tracker positioned so as to observe a right eye of a user, andan ambient light sensor 534. In some embodiments, AR device 500 includesone or more image projection devices such as a left projector 514Aoptically linked to left eyepiece 502A and a right projector 514Boptically linked to right eyepiece 502B.

Some or all of the components of AR device 500 may be head mounted suchthat projected images may be viewed by a user. In one particularimplementation, all of the components of AR device 500 shown in FIG. 5are mounted onto a single device (e.g., a single headset) wearable by auser. In another implementation, one or more components of a processingmodule 550 are physically separate from and communicatively coupled tothe other components of AR device 500 by one or more wired and/orwireless connections. For example, processing module 550 may include alocal module 552 on the head mounted portion of AR device 500 and aremote module 556 physically separate from and communicatively linked tolocal module 552. Remote module 556 may be mounted in a variety ofconfigurations, such as fixedly attached to a frame, fixedly attached toa helmet or hat worn by a user, embedded in headphones, or otherwiseremovably attached to a user (e.g., in a backpack-style configuration,in a belt-coupling style configuration, etc.).

Processing module 550 may include a processor and an associated digitalmemory, such as non-volatile memory (e.g., flash memory), both of whichmay be utilized to assist in the processing, caching, and storage ofdata. The data may include data captured from sensors (which may be,e.g., operatively coupled to AR device 500) or otherwise attached to auser, such as cameras 506, ambient light sensor 534, eye trackers,microphones, inertial measurement units, accelerometers, compasses, GPSunits, radio devices, and/or gyros. For example, processing module 550may receive image(s) 520 from cameras 506. Specifically, processingmodule 550 may receive left front image(s) 520A from left front-facingworld camera 506A, right front image(s) 520B from right front-facingworld camera 506B, left side image(s) 520C from left side-facing worldcamera 506C, and right side image(s) 520D from right side-facing worldcamera 506D. In some embodiments, image(s) 520 may include a singleimage, a pair of images, a video comprising a stream of images, a videocomprising a stream of paired images, and the like. Image(s) 520 may beperiodically generated and sent to processing module 550 while AR device500 is powered on, or may be generated in response to an instructionsent by processing module 550 to one or more of the cameras. As anotherexample, processing module 550 may receive ambient light informationfrom ambient light sensor 534. As another example, processing module 550may receive gaze information from the eye trackers. As another example,processing module 550 may receive image information (e.g., imagebrightness values) from one or both of projectors 514.

Eyepieces 502A, 502B may comprise transparent or semi-transparentwaveguides configured to direct and outcouple light from projectors514A, 514B, respectively. Specifically, processing module 550 may causeleft projector 514A to output left virtual image light 522A onto lefteyepiece 502A, and may cause right projector 514B to output rightvirtual image light 522B onto right eyepiece 502B. In some embodiments,each of eyepieces 502 may comprise a plurality of waveguidescorresponding to different colors and/or different depth planes. In someembodiments, shutter elements 503 may be coupled to and/or integratedwith eyepieces 502. For example, shutter elements 503 may beincorporated into a multi-layer eyepiece and may form one or more layersthat make up one of eyepieces 502. In some embodiments, processingmodule may electrically activate shutter elements 503A, 503B using leftshutter control signals 519A and right shutter control signals 519B,respectively. For example, processing module 550 may apply differentvoltages to shutter control signals 519 to cause AR device 500 toalternate between presenting world light and virtual image light to auser.

Cameras 506A, 506B may be positioned to capture images thatsubstantially overlap with the field of view of a user's left and righteyes, respectively. Accordingly, placement of cameras 506 may be near auser's eyes but not so near as to obscure the user's field of view.Alternatively or additionally, cameras 506A, 506B may be positioned soas to align with the incoupling locations of virtual image light 522A,522B, respectively. Cameras 506C, 506D may be positioned to captureimages to the side of a user, e.g., in a user's peripheral vision oroutside the user's peripheral vision. Image(s) 520C, 520D captured usingcameras 506C, 506D need not necessarily overlap with image(s) 520A, 520Bcaptured using cameras 506A, 506B.

Polarization-Selective Lens Stack Comprising Birefringent Lens andIsotropic Lens for Adaptive Lens Assemblies

Various embodiments described herein provide adaptive lens assembliesthat include a polarization-selective lens stack. In certainimplementations, the polarization-selective lens stack comprises abirefringent lens, e.g., a Fresnel birefringent lens, and an isotropiclens contacting each other. Such assemblies can be compact (e.g., canhave reduced thickness) and/or lightweight. These assemblies maypotentially also provide various advantageous optical functionalitiessuch as high bandwidth, increased switching speeds, reduced chromaticaberrations, increased ease of alignment, and/or variable optical power.In addition, various embodiments described herein can provide adaptivelens assemblies with relatively low amount of leakage light that canotherwise lead to “ghost” images. According to various embodiments,adaptive assemblies comprise a polarization-selective lens stackcomprising a birefringent lens and an isotropic lens, as describedherein.

Referring to FIG. 6A, to provide images at a plurality of depth planeswith high efficiency over a wide range of the visible spectrum, adaptivelens assemblies according to various embodiments include apolarization-selective lens stack 600 configured to exertpolarization-dependent optical power to linearly polarized light.Polarization-selective lens stack 600 may comprise a birefringent lens604 having an optic axis 602 extending in a lateral direction, e.g.,x-direction or y-direction direction, perpendicular to the direction oflight propagation, e.g., the z-direction. Birefringent lens 604 has abirefringence Δn. Birefringence Δn corresponds to a difference betweenan extraordinary refractive index n_(e) and an ordinary refractive indexn_(o) of birefringent lens 604. Birefringent lens 604 can have a radiusof curvature R₁ such that it is configured to exert a first opticalpower p₁ to light passing therethrough and having a polarizationdirection parallel to the optic axis, and to exert a second opticalpower p₂ to light passing therethrough and having a polarizationdirection perpendicular to the optic axis.

Polarization-selective lens stack 600 may additionally include anisotropic lens 608 having a refractive index n_(c), which has a secondradius of curvature R₂ such that it is configured to exert to lightpassing therethrough a third optical power p₃ opposite in sign as thefirst optical power p₁ and the second optical power p₂.

In the illustrated embodiment, without limitation, the extraordinaryrefractive index n_(e) of isotropic lens 608 has substantially the samevalue as the ordinary refractive index n_(o) of birefringent lens 604.However, it will be appreciated that the extraordinary refractive indexn_(e) can be different from the ordinary refractive index n_(o) in someother embodiments.

In the illustrated embodiment, without limitation, the first radius ofcurvature R₁ and the second radius of curvature R₂ are substantially thesame in magnitude R while having opposite signs. Furthermore, because R₁and R₂ are substantially the same in magnitude, birefringent lens 604and isotropic lens 608 make continuous contact along the interfacehaving the radius of curvature R. That is, the contacting surfaces ofbirefringent lens 604 and isotropic lens 608 form a conformal interfacetherebetween.

With reference to FIG. 6B, polarization-selective lens stack 600 isillustrated in operation when an incident light 612, e.g., linearlypolarized light, has a direction of polarization that is parallel to thedirection of optic axis 602. Under this condition, because light passingthrough birefringent lens 604 experiences a refractive indexcorresponding to extraordinary refractive index n_(e) and light passingthrough isotropic lens 608 experiences a refractive index correspondingto ordinary refractive index n_(o), lens stack 600 exerts an opticalpower to the light that can be expressed as:

$\varphi_{1} = {\frac{n_{e} - n_{0}}{R} = \frac{\Delta n}{R}}$

where R represents the magnitude of radii of birefringent lens 604 andisotropic lens 608.

With reference to FIG. 6C, polarization-selective lens stack 600 isillustrated in operation when an incident light 616, e.g., linearlypolarized light, has a direction of polarization that is perpendicularto the direction of optical axis 602. Under this condition, becauselight passing through birefringent lens 604 experiences a refractiveindex corresponding to ordinary refractive index n_(o), which is thesame as the refractive index experienced by light passing throughisotropic lens 608, lens stack 600 exerts an optical power to the lightthat can be expressed as:

$\varphi_{1} = {\frac{n_{e} - n_{0}}{R} \cong \frac{\Delta n}{R}}$

where R represents the magnitude radii of birefringent lens 604 andisotropic lens 608.

Still referring to FIGS. 6A-6C, in some embodiments, isotropic lens 608may be formed of an isotropic material, e.g., glass, acrylic, etc. Onthe other hand, birefringent lens 604 may be formed of or comprises abirefringent material, e.g., liquid crystals according to variousembodiments. For example, birefringent lens 604 may comprise atransparent substrate e.g., a glass substrate, having formed thereonliquid crystal (LC) molecules that are elongated along a lateraldirection (e.g., x-direction or y-direction) perpendicular to the lightpropagation direction (e.g., z-direction).

However, embodiments are not so limited and in other embodiments,birefringent lens 604 may be formed of or comprises a suitablebirefringent material other than LCs. For example, birefringent lens 604may comprise, e.g., BaB₂O₄, Be₃Al₂(SiO₃)₆, CaCO₃LiNbO₃TiO₂SiC,tourmaline and ZrSiO₄ to name a few.

Polarization-Selective Lens Stack Comprising a Birefringent Fresnel Lensand Isotropic Lens for Adaptive Lens Assemblies

As described above with respect to FIGS. 6A-6C, a lens stack comprisinga birefringent lens, e.g., LC-based birefringent lens, and an isotropiclens can provide polarization-selective lensing effect. In thefollowing, a polarization-selective lens stack comprising a liquidcrystal-based birefringent lens configured as a Fresnel lens isdescribed.

A Fresnel lens can for example comprise a thin-plate type of lens, whichcomprises fractional prismatic structures formed by breaking aconventional curved (e.g., spherical) lens into a set of sections, e.g.,concentric annular sections, known as Fresnel zones. The Fresnel zonesreplace the continuous curvature of a continuous refractive lens with aset of surfaces of the same shape having discontinuities between them. Asubstantial reduction in thickness can be achieved by employing suchfractional sections and lenses with a relatively large aperture can bemanufactured using a smaller volume of material.

FIG. 7A illustrates a cross-sectional side view of lens stack 600described above with respect to FIGS. 6A-6C, annotated with relevantoptical dimensions including the distance R to a given location onbirefringent lens 604 from the focal point, the radial distance A to thegiven location from a central axis (e.g., optical axis) of lens stack600, the angle θ defined by the distances R and A, and the thickness dof the curved portion of birefringent lens 604. As described above, invarious implementations, because birefringent lens 604 and isotropiclens 608 have substantially the same radius of curvature, birefringentlens 604 and isotropic lens 608 make continuous contact along theinterface formed therebetween having the radius of curvature R.

FIG. 7B illustrates a cross-sectional side view 700A (top) and a topdown view 700B (bottom) of a lens stack 700 comprising a birefringentFresnel lens 704 and a counterpart lens, e.g., an isotropic Fresnel lens708. By employing the Fresnel lens 704, the groove thickness d′ of thecurved portion of birefringent lens 704 can be substantially reduced.Despite the substantially reduced thickness d′, lens stack 700 has acorresponding curvature such as effective radius of curvature Rcorresponding to the actual radius of curvature R of the conventionallens illustrated with respect to FIG. 7A. Accordingly, while notillustrated, lens stack 700A additionally has a radial distance A_(k) ofa given Fresnel zone or a groove 706 from a central axis of lens stack700 and the angle θ defined by the distances R and A_(k). In someimplementations such as shown in FIG. 7B, despite the grooves separatingthe Fresnel zones, birefringent Fresnel lens 704 and isotropic lens 708make continuous contact throughout the interface formed therebetweenhaving the effective radius of curvature R. In some embodiments,successive Fresnel zones in the radially outward direction can havedifferent radial distances A_(k) and different distances betweenadjacent grooves 706. For example, in the illustrated embodiment, thedistances between adjacent Fresnel zones become smaller in the radiallyoutward direction of birefringent Fresnel lens 704. However, embodimentsare not so limited and in other embodiments, the radial distances A_(k)of successive Fresnel zones can increase linearly with constantdistances between adjacent Fresnel zones while having different groovethicknesses within each zone to provide similar or same optical effectsas the illustrated embodiment.

Referring to FIG. 7B (bottom), the illustrated birefringent Fresnel lens704 comprises a plurality of concentric Fresnel zones according to someembodiments. The birefringent Fresnel lens 704 has a plurality ofgrooves 716 forming boundaries of Fresnel zones 712 at distances fromthe central axis represented by radii A_(k). According to variousembodiments, the groove thickness d′ of the birefringent lens 704 isdesigned such that the path length is a multiple of the designwavelength λ. This arrangement can create a 2 nm phase jump between thezones that leads to the same wavefront. The value of d′ can be chosen(e.g., optimized) to balance fabrication tolerances and to reduce orminimize aberrations that can arise from sharp edges of grooves 716. Inone example, the radius R, of the k^(th) Fresnel zone can be calculatedby setting the thickness of the curved region to be kd′, by thefollowing equation:

$A_{k} = \sqrt{\frac{2\Delta\;{nfkm}\;\lambda}{n_{0}} - \left( \frac{k\; m\;\lambda}{n_{0}} \right)^{2}}$

where k represents the number of the Fresnel zone counting from thecenter of the lens, and where the groove thickness d′ is constant acrossthe surface of the illustrated birefringent Fresnel lens 704.

In some embodiments, birefringent Fresnel lens 704 includes LCs. The LCmolecules may be laterally aligned, or have elongation directionsextending, substantially in a lateral direction 720 indicated by thearrow (e.g., y direction). In addition, the alignment directions of theLC molecules may be substantially homogenous throughout the thickness ofbirefringent Fresnel lens 704 without undergoing rotation. That is, thelocal director n of the LC molecules may be substantially constantlaterally across the area and vertically across the thickness (e.g., inz direction) of the birefringent Fresnel lens 704. The illustratedalignment may be suitable, e.g., for providing polarization selectivityfor linearly polarized light. In these embodiments, linearly polarizedlight having polarization direction that is parallel to the direction ofLC alignment (e.g., y direction) may experience one of n_(e) or n_(o),while linearly polarized light having polarization direction that isperpendicular to the direction of LC alignment (e.g., x direction) mayexperience the other of n_(e) or n_(o). As a result, lens stack 700exerts an optical power of Δn/R for light having one linear polarizationwhile exerting a substantially zero optical power for light having theother linear polarization, as described above.

In various embodiments herein and throughout the specification, thebirefringent Fresnel lens 704 can have an average, a local, a mean, amedian, a maximum or a minimum birefringence Δn of 0.05-0.10, 0.15-0.20,0.20-0.25, 0.25-0.30, 0.30-0.35, 0.35-0.40, 0.40-0.45, 0.45-0.50,0.50-0.55, 0.55-0.60, 0.60-0.65, 0.65-0.70, or any value within anyrange defined by any of these values, for instance 0.05-0.40. Inaddition, birefringent Fresnel lens 704 can a have a within-layerbirefringence (Δn) range of 0.01-0.05, 0.05-0.10, 0.15-0.20, 0.20-0.25,0.25-0.30, 0.30-0.35, 0.35-0.40, or any value within any range definedby any of these values.

In various embodiments herein and throughout the specification,birefringent Fresnel lens 704 has a thickness of about 0.1 μm-200 μm,0.1-5 μm, 5-50 μm, 50-100 μm, 100-150 μm, 150-200 μm, or a value withinany range defined by these values, for instance 5-200 μm.

Adaptive Lens Assemblies Comprising Polarization-Selective Lens StackCoupled with Switchable Waveplate

To provide images at a plurality of depth planes with high efficiencyover a wide range of the visible spectrum, adaptive lens assembliesaccording to various embodiments include a polarization-selective lensstack (e.g., 600 in FIGS. 6A-6C, 700 in FIG. 7B) comprising abirefringent lens and an isotropic lens. According to variousembodiments, adaptive lens assemblies can be selectively switchedbetween a plurality of states with different optical powers. In thefollowing, adaptive lens assemblies are disclosed, in which theselective switching is performed by activating or deactivating aswitchable waveplate coupled to a polarization-selective lens includedin the adaptive lens assembly according to embodiments.

Referring to FIG. 8A, in some embodiments, an adaptive lens assembly800A is configured to be activated or deactivated by employing aswitchable waveplate 804 comprising LCs in the same optical path aspolarization-selective lens stack 700 described above comprisingbirefringent Fresnel lens 704 and isotropic lens 708. Fresnel lens 704may be formed using LCs or other birefringent materials. Adaptive lensassembly 800A may be selectively switched between different states byelectrically activating and deactivating switchable waveplate 804 (orotherwise changing the states of the waveplate, e.g., by applyingdifferent voltages). One example of the switchable waveplate 804 isillustrated with respect to FIG. 8B.

Referring to FIG. 8B, in some embodiments, switchable waveplate 802 maybe a half waveplate or a polarization rotator comprising a layer 802 ofunpolymerized twisted nematic (TN) liquid crystals (LCs), or reactivemesogens (RM) comprising TN LC molecules, which is configured to beswitched upon application of an electric field across a thickness oflayer 802 of TN LCs. Layer 802 of TN LCs is disposed between a pair oftransparent substrates 812. Each of transparent substrates 812 hasformed on the inner surface a conducting transparent electrode 816, 820.In some embodiments, transparent electrodes 816, 820 may serve assubstrates, and one or both of substrates 812 may be omitted.

The surfaces of transparent electrodes 816, 820 and/or substrates 812may be configured such that the TN LC molecules in contact with orimmediately adjacent to upper electrode 816 tend to orient with theirlong axes extending in a first lateral direction, while the TN LCmolecules in contact with or immediately adjacent to lower electrode 820tend to orient with their long axes extending in a second lateraldirection, which may cross, e.g., to form an angle of about 90 degreesrelative to, the first lateral direction. Accordingly, the TN LCmolecules between electrodes 816, 820 undergo a twist.

Still referring to FIG. 8B (left), in operation, in the absence of anelectric field (deactivated state) across TN LC layer 802, the nematicdirector of the TN LC molecules undergoes a smooth 90 degree twistacross the thickness of TN LC layer 802. As illustrated, incident light808 polarized in a first direction (same direction as the LC moleculesclosest to lower electrodes 812) is incident on the TN LC layer 802. Thetwisted arrangement of the TN LC molecules within TN LC layer 802 servesas an optical wave guide and rotates the plane of polarization by aquarter turn (90 degrees) prior to the light reaching upper electrodes816. In this state, TN LC layer 802 serves to shift the polarizationdirection of linearly polarized light passing therethrough from onelinear polarization direction to another. Thus, transmitted light 806Ais polarized in a second direction (same direction as the LC moleculescloses to upper electrodes 816) opposite the first direction.

On the other hand, when a voltage exceeding a threshold voltage (V>Vth)of TN LC switchable waveplate 804 is applied to across electrodes 816,820 (right, activated state), the TN LC molecules within TN LC layer 802tend to align with the resulting electric field and the optical waveguiding property of TN LC layer 802 described above with respect to thedeactivated state is lost. In this state, TN LC layer 802 serves topreserve the polarization direction of light passing therethrough. Thus,incident light 808 and transmitted light 806B are polarized in the samefirst direction (same direction as the LC molecules closest to lowerelectrodes 820). When the electric field is turned off, the TN LCmolecules relax back to their twisted state and the TN LC molecules ofTN LC layer 802 in the activated state returns to the configuration ofTN LC molecules of TN LC layer 802 in the deactivated state (left).

Still referring to FIG. 8A, in operation, as described above,polarization-selective lens stack 700 exerts a lens power to incidentlight 820 passing therethrough depending on the polarization directionof incident light 820. After having or not having exerted optical powerthereto, depending on the relative polarization direction of theincident light, the light is incident on switchable waveplate 804. Asdescribed above, the LCs of switchable waveplate 804 are configured suchthat, when activated, e.g., electrically activated, the polarization ofa linearly polarized light passing therethrough is preserved, while whendeactivated, e.g., electrically deactivated, the polarization of thelinearly polarized light passing therethrough is altered, e.g., flippedor rotated. That is, a linearly vertical polarized (LVP) light beam isconverted to a linearly horizontal polarized (LHP) light beam and viceversa, or the polarization is preserved, depending on whether switchablewaveplate 804 is activated or deactivated.

In operation, the LCs of birefringent Fresnel lens 704 are configuredsuch that, when the polarization direction of linearly polarizedincident light 820 is parallel to the optic axis of birefringent Fresnellens 704, polarization-selective lens stack 700 exerts an optical powerthereto, as described above with respect to FIG. 6B, while when thepolarization direction of linearly polarized incident light 820 isperpendicular to the optic axis, polarization-selective lens stack 700exerts substantially zero optical power thereto, as described above withrespect to FIG. 6C. After passing through birefringent lens stack 700,when activated, e.g., electrically activated, the polarization of alinearly polarized light passing through the switchable waveplate 804 ispreserved, while when deactivated, e.g., electrically deactivated, thepolarization of the linearly polarized light passing through switchablewaveplate 804 is flipped or rotated, due to rearrangement of liquidcrystal molecules.

With respect to FIGS. 8A-8B, adaptive lens assemblies comprising apassive polarization-selective lens stack coupled with a waveplate (FIG.8A) for switchably exerting lens power have been described. Theinventors have recognized that, by arranging a plurality of suchelements, adaptive lens assemblies having a plurality of different lenspowers can be formed. Thus, in the following, embodiments of adaptivewaveplate lens assemblies comprising a plurality of passivepolarization-selective lens stacks coupled with waveplates aredisclosed. Such adaptive lens assemblies may be integrated with awaveguide either on the user side or the world side, to form displaydevices described with respect to, e.g., FIGS. 3A and 3B.

FIG. 9A illustrates an example of an adaptive lens assembly 900comprising a plurality of passive polarization-selective lens stacks anda plurality of waveplates that are alternatingly arranged to exert aplurality, e.g., at least four, possible optical powers to light passingtherethrough. Adaptive lens assembly 900 comprises, in the order oflight passing therethrough, a first switchable waveplate (HWP1) 804-1,e.g., a half waveplate, a first polarization-selective lens stack (L1)700-1, a second switchable waveplate (HWP2) 804-2, e.g., a halfwaveplate, and a second polarization-selective lens stack (L2) 700-2.Each of HWP1 804-1 and HWP2 804-2 is configured in a manner similar tothat described above with respect to FIGS. 8A and 8B. In addition, eachof L1 700-1 and L2 700-2 is configured in a similar manner to thatdescribed above with respect to FIGS. 6A-6C, 7A-7B and 8A-8B. However,first and second polarization-selective lens stacks 700-1, 700-2 havedifferent optic axes, different curvature (e.g., effective radii ofcurvature) and/or different birefringence. That is, L1 700-1 has a firstoptic axis (extending in a vertical or y direction) and is configured toexert a first optical power ϕ₁ of Δ_(n1)/R₁ or substantially zero tolight incident thereon having a polarization direction parallel orperpendicular to the optic axis, respectively, while the 700-2 has asecond optic axis (extending in a horizontal or x-axis) and isconfigured to exert a second optical power ϕ₂ of Δn₂/R₂ or substantiallyzero to light incident thereon having a polarization direction parallelor perpendicular to the optic axis, respectively.

FIGS. 9B-9E illustrate the adaptive lens assembly 900 in operation, forincident light 820 having a polarization parallel to the optic axis ofL1 700-1, at four different states corresponding to HWP1 804-1/HWP 804-2being deactivated (OFF)/deactivated (OFF) (FIG. 9B), activated(ON)/activated (ON) (FIG. 9C), OFF/ON (FIG. 9D), and ON/OFF (FIG. 9E).As described above, each of HWP1 804-1 and HWP2 804-2 can be turned OFFand ON, or deactivated and activated, by removing and applying a voltageacross the TN LC layer. Each of HWP1 804-1 and HWP2 804-2 is configuredto alter a polarization state, e.g., rotate or invert a polarizationstate, of light passing therethrough when electrically deactivated(OFF), while being configured to substantially pass light withoutaltering the polarization state of light passing therethrough whenactivated (ON). The electrical signal, e.g., a current signal or avoltage signal, for switching each of HWP1 804-1 and HWP2 804-2 may beprovided by a switching circuit (not shown) electrically connectedthereto. For illustrative purposes, in the following, both HWP1 804-1and HWP2 804-2 are TN LC cells having optic axes along the y and xdirections at their two substrates respectively, similar to FIG. 8B. Inthe illustrated embodiment, the incident light 820 has a polarizationparallel to y direction, i.e., a linear vertical polarization (LVP).However, it will be appreciated that the polarization axis of incidentlight 820 can be polarized in a different direction, a linear horizontalpolarization (LHP), to achieve the different optical power states.

Referring to FIG. 9B, each of HWP1 804-1 and HWP2 804-2 are in the OFFstate and configured to rotate the polarization of linearly polarizedlight having one of LVP and LHP into linearly polarized having the otherof LVP and LHP. Thus, incident light 820 having LHP, upon passingthrough HWP1 804-1, is converted to light 824 incident on L1 700-1having LHP, which exerts substantially zero optical power (ϕ₁=0) due tothe relative orthogonal orientations between the polarization of light824 and the optic axis of the L1 700-1. Thereafter, light 828 having LHPincident on HWP2 804-2 is converted to light 832 having LVP. L2 700-2exerts substantially zero optical power (ϕ₂=0) due to the relativeorthogonal orientations between the polarization of L2 700-2 and theoptic axis of L2 700-2. In sum, adaptive lens assembly 900 exerts a netpower ϕ₁+ϕ₂ equal to about zero to the incident light 820 having LVP anddoes not alter its polarization, thereby outputting light 836 havingLVP.

Referring to FIG. 9C, each of HWP1 804-1 and HWP2 804-2 are in the ONstate and configured to preserve the polarization of linearly polarizedlight passing therethrough. Thus, the polarization of incident light 820having LVP, upon passing through HWP1 804-1, is preserved into light 824incident on L1 700-1, which exerts an optical power (ϕ₁) due to therelative parallel orientations between the polarization of light 824 andthe optical axis of L1 700-1. Thereafter, the polarization of light 828having LVP incident on HWP2 802-2 is preserved into light 832. L2 700-2exerts substantially zero optical power (ϕ₂=0) due to the relativeorthogonal orientations between the polarization of light 832 and theoptic axis of L2 700-2. In sum, adaptive lens assembly 900 exerts a netpower ϕ₁+₂ equal to about ϕ₁ to incident light 820 having LVP andoutputs light 836 having LVP.

Referring to FIG. 9D, HWP1 804-1 is in the OFF state and configured torotate the polarization of linearly polarized light having one of LVPand LHP into linearly polarized having the other of LVP and LHP, whileHWP2 804-2 is in the ON state and configured to preserve thepolarization of linearly polarized light. Thus, incident light 820having LVP, upon passing through HWP1 804-1, is converted to light 824incident on L1 700-1 having LHP, which exerts substantially zero opticalpower (ϕ₁=0) due to the relative orthogonal orientations between thepolarization of light 824 and the optic axis of L1 700-1. Thereafter,the polarization of light 828 having LHP passing through HWP2 802-2 ispreserved into light 832. The light 832 incident on L2 700-2 has LHP,which exerts an optical power (ϕ₂) due to the relative parallelorientations between the polarization of light 832 and the optic axis ofL2 700-2. In sum, adaptive lens assembly 900 exerts a net power ϕ₁+ϕ₂equal to about ϕ₂ to incident light 820 having LVP and outputs light 836having LHP.

Referring to FIG. 9E, HWP1 804-1 is in the ON state and configured topreserve the polarization of linearly polarized light, while HWP2 804-2is in the OFF state and is configured to rotate the polarization oflinearly polarized light having one of LVP and LHP into linearlypolarized having the other of LVP and LHP. Thus, the polarization ofincident light 820 having LVP, upon passing through HWP1 804-1, ispreserved into light 824 incident on L1 700-1 having LVP, which exertsan optical power (ϕ₁) due to the relative parallel orientations betweenthe polarization of light 824 and the optic axis of L1 700-1.Thereafter, light 828 having LVP passing through HWP2 804-2 is convertedinto light 832 having LHP. L2 700-2 exerts an optical power (ϕ₂) due tothe relative parallel orientations between the polarization of light 832and the optic axis of L2 700-2. In sum, adaptive lens assembly 900exerts a net power ϕ₁+ϕ₂ to incident light 820 having LVP and outputslight 836 having LHP.

Thus, as illustrated by FIGS. 9A-9E, for light with linear polarization,four possible net powers (0, ϕ₁, ϕ₂. and ϕ₁+ϕ₂) can be exerted on thelight passing though the adaptive lens assembly 900. By way of anumerical example, for ϕ₁=0.75 D and ϕ₂=1.5 D for the design wavelength,net optical powers of 0, 0.75 D, 1.5 D, and 2.25 D can be obtained usingadaptive lens assembly 900.

Still referring to FIGS. 9A-9E in conjunction with FIGS. 3A and 3B, inthe illustrated embodiment, incident light 820 may represent a lightbeam incident on either world-side adaptive lens assembly 204 oruser-side adaptive lens assembly 208. By placing adaptive lens assembly900 on either or both sides, display systems described above, e.g., withrespect to FIGS. 3A and 3B, can be implemented, according to variousembodiments as described herein.

Display Devices Including Adaptive Lens Assemblies HavingPolarization-Selective Lens Stack Coupled to Nonpolarizing WaveguideAssembly

In the following example implementations, an adaptive lens assemblycomprising a plurality of switchable polarization-selective lens stacks(e.g., adaptive lens assembly 900, FIGS. 9A-9E) has been integrated intoa display device, such as for example, a display device such asdescribed supra with respect to FIGS. 2, 3A, and 3B.

FIG. 10 illustrates an example display device 1000 including a waveguideassembly 1012 interposed between a first or front adaptive lens assembly(FLA) 1004 and a second or back adaptive lens assembly (BLA) 1008.Display device 1000 can be similar to display devices 300A, 300Bdescribed above with respect to FIGS. 3A and 3B. In the illustratedembodiment, BLA 1008 is configured similarly to adaptive lens assembly900 described above with respect to FIGS. 9A-9E, and includes a firstswitchable waveplate (HWP1) 804-1, a first polarization-selective lensstack (L1) 700-1, a second switchable waveplate (HWP2) 804-2 and asecond polarization-selective lens stack (L2) 700-2. First and secondpolarization-selective lens stacks 700-1, 700-2 have different, e.g.,orthogonal optic axes, curvature (e.g., effective radii of curvature)and/or different birefringence, such that L1 700-1 is configured toexert a first optical power ϕ₁ of n₁/R₁ or substantially zero for lightincident thereon having a polarization direction parallel orperpendicular to the optic axis, respectively, while L2 700-2 isconfigured to exert a second optical power ϕ₂ of n₂/R₂ or substantiallyzero for light incident thereon having a polarization direction parallelor perpendicular to the optic axis, respectively.

FLA 1004 includes a third switchable waveplate (HWP3) 804-3, a thirdpolarization-selective lens stack (L3) 700-3, a fourth switchablewaveplate (HWP4) 804-4 and a fourth polarization-selective lens stack(L4) 700-4. Third and fourth polarization-selective lens stacks 700-3,700-4 have different, e.g., orthogonal optical axes, effective radii ofcurvature and/or different birefringence, such that L3 700-3 isconfigured to exert a third optical power ϕ₃ of n₃/R₃ or substantiallyzero to light incident thereon having a polarization direction parallelor perpendicular to the optic axis, respectively, while the L4 700-4 isconfigured to exert a fourth optical power ϕ₄ of n₄/R₄ or substantiallyzero to light incident thereon having a polarization direction parallelor perpendicular to the optic axis, respectively.

In various embodiments, the effective radii of curvature of L1 700-1 andL2 700-2 are such that the ϕ1 and ϕ2 have a first sign, e.g., positivesign, while the effective radii of curvature of L3 700-3 and L4 700-4are such that the ϕ₃ and ϕ₄ have a second sign opposite the first sign,e.g., negative sign. That is, when the three possible non-zero netpowers (ϕ₁, ϕ₂. and ϕ₁+ϕ₂) of FLA 1004 may have one of converging ordiverging effects (e.g., converging), the three possible non-zero netpowers (ϕ₃, ϕ₄. and ϕ₃+ϕ₄) of BLA 1008 may have the other of convergingor diverging effects (e.g., diverging). In the illustrated embodiment,FLA 1004 and BLA 1008 are configured to be substantially the same,except for the curvatures of the interface between the birefringent andisotropic lenses (e.g., one is concave and other is convex or viceversa, etc.). In particular, FLA 1004 and BLA 1008 form mirror imagesabout waveguide assembly 1012. Thus, as configured, L1 804-1 and L3804-3 have optical powers ϕ₁ and ϕ₃, respectively, that aresubstantially the same in magnitude but opposite in sign, and L2 804-2and L4 804-4 have optical powers ϕ₂ and ϕ₄, respectively, that aresubstantially the same in magnitude but opposite in sign. That is, ϕ₁ isapproximately equal to −ϕ₃, and ϕ₂ is approximately equal to −ϕ₄.

Still referring to FIG. 10, in the illustrated embodiment, waveguideassembly 1012 is configured to outcouple unpolarized light that has beentotally internally reflected. In this configuration, display device 1000additionally includes a linear polarizer 1005 between waveguide assembly1012 and BLA 1008 configured to reduce or eliminate, e.g., reflect orabsorb, light having polarization state that does not lead to lensaction by BLA 1008. For example, in arrangements where light 1009outcoupled from waveguide assembly 1012, or light 1020 transmittedthrough FLA 1004 unaffected is not linearly polarized, e.g., not LVP,linear polarizer 1005 serves to linearly polarize the transmitted lightto feed incident light 820 into BLA 1008.

As configured, BLA 1008 serves to provide variable optical powers (ϕ₁,ϕ₂, and ϕ₁+ϕ₂) to form images at a plurality of depth planes for thevirtual images exiting waveguide assembly 1012 towards the eye of theuser. While BLA 1008 provides virtual images by focusing images fromwaveguide assembly 1012 at a plurality of depth planes, the world imagecan be distorted by BLA 1008. FLA 1004 serves to compensate thedistortion of the world image caused by BLA 1008 by providing variableoptical powers (ϕ₃=−ϕ₁, ϕ₄=ϕ−₂, and ϕ₃+ϕ₄=−(ϕ₁+ϕ₂)), such that the worldimage is presented to the eye of the user without substantialdistortion.

In various embodiments, e.g., when deactivated, each of FLA 1004 and BLA1008 may provide a net optical power (positive or negative) in the rangebetween about ±5.0 diopters and 0 diopters, ±4.0 diopters and 0diopters, ±3.0 diopters and 0 diopters, ±2.0 diopters and 0 diopters,±1.0 diopters and 0 diopters, including any range defined by any ofthese values, for instance ±1.5 diopters. In some embodiments, FLA 1004between waveguide assembly 1012 and the world may have a positiveoptical power, whereas BLA 1008 between waveguide assembly 1012 and theuser may have a negative optical power, such that the optical powers ofFLA 1004 and BLA 1008 compensate each other in viewing the world.

As described supra, as the images of virtual objects produced by lightoutcoupled by waveguide assembly 1012 move in 3D, the net optical powerof BLA 1008 on the user side is adjusted to adapt to the changing depthof the virtual depth plane. Simultaneously, according to embodiments,the net optical power of FLA 1004 is correspondingly adjusted using aswitching circuit, such that the view of the real world does notundesirably become defocused or distorted. To address this and otherneeds, in some embodiments, display device 1000 comprises a controller(not shown) configured such that, when the net optical power of one ofFLA 1004 and BLA 1008 is electrically adjusted, the net optical power ofthe other of FLA 1004 and BLA 1008 is correspondingly adjusted such thatthe combined net optical powers remain about constant, e.g., about zero.The controller circuitry and the switchable waveplates are configuredsuch that the time to switch HWP1 804-1, HWP2 804-2, HWP3 804-3 and HWP4804-4, to adjust the virtual depth planes using user-side adaptive lensassembly 1008 and to compensate the real world view using user-sideadaptive lens assembly 1004, is less than about 100 milliseconds, lessthan about 50 milliseconds, less than about less than about 10milliseconds, less than about 5 milliseconds, less than about 1millisecond, or a value within a range defined by any of these values.

Display Devices Including Adaptive Lens Assemblies HavingPolarization-Selective Lens Stack Coupled to Polarizing WaveguideAssembly

FIG. 11A illustrates an example display device 1100 according to someembodiments. Similar to the display device described above with respectto FIG. 10, display device 1100 includes a second adaptive lens assembly(BLA) 1008 that includes a first switchable waveplate (HWP1) 804-1, afirst polarization-selective lens stack (L1) 700-1, a second switchablewaveplate (HWP2) 804-2 and a second polarization-selective lens stack(L2) 700-2. However, unlike the display device described above withrespect to FIG. 10, display device 1100 includes a polarizing waveguideassembly 1112 that outcouples polarized light 1108, e.g., circularlypolarized light, into the BLA 1008. Accordingly, BLA 1008 additionallyincludes a first quarter waveplate (QWP1) 1104, e.g., an achromaticquarter waveplate, configured to convert RHCP light 1108-R and LHCPlight 1108-L, outcoupled from the polarizing waveguide assembly 1112into linear polarized light 820 incident on BLA 1008. Thus, BLA 1008operates in a similar manner as described above with respect to FIG. 10.

However, unlike display device 1000 of FIG. 10, display device 1100 doesnot have a FLA 1004 configured to compensate or cancel undesirableoptical power exerted by BLA 1008 to world-side light 1020 when BLA 1008exerts optical power to light from polarizing waveguide assembly 1112containing virtual image information. Instead, display device 1100 isconfigured to alternatingly display world image and virtual image. Thisis achieved by replacing FLA 1004 (FIG. 10) with a combination of ashutter 1120, a linear polarizer 1116 and a second quarter waveplate(QWP2) 1114, e.g., an achromatic quarter waveplate. In the following,polarizing waveguide assembly 1112 is described with respect to FIG.11B, followed by the operational principles of display device 1100 withrespect to FIGS. 11C and 11D.

FIG. 11B illustrates an example of polarizing waveguide assembly 1112,according to embodiments. In some embodiments, polarizing waveguideassembly 1112 is configured to output circularly polarized light, e.g.,right-handed (RHCP) or left-handed (LHCP) circular polarized light. Invarious embodiments, polarizing waveguide assembly 1112 may comprisecholesteric liquid crystal (CLC) layers and/or CLC gratings (CLCGs),which in turn comprise liquid crystals arranged to have a plurality ofchiral structures. Each of the chiral structures comprises a pluralityof liquid crystal molecules that extend in a layer depth direction by atleast a helical pitch and are successively rotated in a rotationdirection. The CLC layers or CLCGs can advantageously be configured tosubstantially Bragg-reflect elliptically or circularly polarized lighthaving a handedness of polarization that is matched to the rotationdirection of the liquid crystal molecules, while being configured tosubstantially transmit elliptically or circularly polarized light havinga handedness of polarization that is opposite to the rotation directionof the liquid crystal molecules. Based on these properties of the CLClayers and CLCGs, various embodiments of display devices disclosedherein have a polarizing waveguide assembly 1112 comprising one or moreCLC layers or CLCGs. Polarizing waveguide assembly 1112 may include aCLCG 1150 configured as an outcoupling optical element, such as an exitpupil expander (EPE), according to embodiments. Polarizing waveguideassembly 1112 comprises a waveguide 1104 coupled to a CLCG 1150 andconfigured to propagate light by total internal reflection (TIR).

Still referring to FIG. 11B, the liquid crystal molecules of theillustrated CLCG 1150 are successively rotated in a rotation direction,and arrangements of the liquid crystal molecules of the chiralstructures vary periodically in a lateral direction (x,y directions)perpendicular to the layer depth direction (z direction). Because of therotational arrangement of the liquid crystal molecules, when light 2604is an elliptically/circularly polarized light having a polarizationhandedness, e.g., one of left-handedness or right-handedness, whichmatches the direction of rotation of the liquid crystal molecules of thechiral structures, light 2604 is Bragg-reflected by CLCG 1150. That is,the rotational arrangement of the liquid crystal molecules in CLCG 1150is such that, CLCG 1150 selectively Bragg reflects light having onehandedness while non-Bragg reflecting or transmitting light having theopposite handedness. In addition, because Bragg reflection occurs underthe diffraction condition, the Bragg reflected light 1108 isunidirectional (e.g., most of the light is directed toward one directionat outcoupling, such as the direction indicated by the arrows 1108 inFIG. 11B). The outcoupled light can preserve a uniform polarizationstate, which corresponds to the chirality of the CLC material. Thus,when configured as an optical outcoupling element, CLCG 1150 serves as apolarizer and a unidirectional reflector, which allows for efficientintegration with other optical components within display device 1100.

As described above, display device 1100 is configured to alternatinglydisplay world image (FIG. 11C) and virtual image (FIG. 11D). Referringto FIG. 11C, when displaying the world image, display device 1100 has aconfiguration 1100C in which both shutter 1120 and waveguide assembly1112 are in the OFF state. In addition, both of HWP-1 820-1 and HWP-2820-2 are in the ON state and OFF state, respectively. As configured,BLA 1008 is configured analogously to state 900B described above withrespect to FIG. 9B. Under this configuration, light 1020 from the world,which is unpolarized, is transmitted through the shutter 1120essentially unaffected and is linearly polarized, e.g., horizontallylinearly polarized (LHP) into light 1124 by linear polarizer 1116. Light1124 is converted to circularly polarized light 1108-L, e.g., LHCPlight, which is incident on the polarizing waveguide assembly 1112.Light 1108-L passes through polarizing waveguide assembly 1112 in theOFF state essentially unaffected, and is converted by QWP1 1104 intolinearly polarized light 820-2 that is linearly polarized, e.g., LHP.BLA 1008 is configured to exert substantially zero optical power,analogously to the state described above with respect to FIG. 9B,thereby passing light 820-2 essentially unaffected to be seen by theeye.

Referring to FIG. 11D, when displaying the virtual image, the displaydevice has a configuration 1100D in which both shutter 1120 andwaveguide assembly 1112 are in the ON state. Thus, any light 1020 fromthe world side is blocked, e.g., reflected. Thus, display deviceconfiguration 1100D is configured to display substantially only thevirtual content outcoupled from polarizing waveguide assembly 1112described above with respect to FIG. 11B. Light 1108-R having a circularpolarization, e.g., RHCP, is incident on QWP2 1104, and BLA 1008 isconfigured analogously to one of states 900C-900E described above withrespect to FIGS. 9C-9E. Under this configuration, circularly polarizedlight 1108-R is transformed by QWP2 1104 into linearly polarized light820-1 having a polarization direction, e.g., vertical polarizationdirection (LVP). BLA 1008 then exerts an optical power according to oneof states 900C-900E described above with respect to FIGS. 9C-9E.

As described, display device 1100 is configured to sequentially displayworld images and virtual images. To display both the world images andthe virtual images to a user as if they were simultaneously presented,configurations 1100C (FIG. 11C) and 1100D (FIG. 11D) are timemultiplexed with respect to each other at a suitable frequency such thathuman eyes perceive them as being essentially simultaneous. For example,shutter 1120 and HWP-1 820-1 and HWP-2 820-2 are alternated at afrequency at-least twice as fast as the video refresh rate to minimizeany switching artifacts. Advantageously, display device 1100 can reducethe overall number of optical elements by replacing FLA 1008 in displaydevice 1000. To compensate for reduction in intensity of the virtualimage due to the multiplexing and polarization, the intensity ofoutcoupled light 1108-R can be accordingly adjusted according toembodiments.

Display Devices Including World-Side and/or User-Side Shutter Elementsand User-Side Lens Assembly

FIG. 12A illustrates an example of a display device 1200 having a singleadaptive lens assembly 1208 on the user side of an eyepiece 1212 (theside of eyepiece 1212 closest to the eye of the user), according to someembodiments of the present disclosure. Lens assembly 1208 may include avariable focal element (VFE) assembly and may be configured to applypositive, negative, or zero optical power to the light passing throughit. Display device 1200 may include one or more world-side shutterelements 1204 coupled to the world side of eyepiece 1212 (the side ofeyepiece 1212 furthest from the eye of the user and closest to worldobjects), and one or more user-side shutter elements 1202 coupled to theuser side of eyepiece 1212. By sequentially electrically activatingworld-side shutter elements 1204 and user-side shutter elements 1202 asdescribed herein, world light 432 may pass through display device 1200with zero net optical power being applied by lens assembly 1208 andvirtual image light 423 may pass through with non-zero (e.g., negative)net optical power being applied by lens assembly 1208.

In the illustrated embodiment, world-side shutter elements 1204 includea world-side polarizer 1216 and a world-side switchable waveplate 1220.World-side polarizer 1216 may be positioned closer to world objects 430such that world light 432 passes first through world-side polarizer 1216prior to passing through world-side switchable waveplate 1220. Uponpassing through world-side polarizer 1216, world light 432 is linearlypolarized along a first axis. Accordingly, world-side polarizer 1216 maycomprise a linear polarizer. After passing through world-side polarizer1216, world light 432 passes through world-side switchable waveplate1220. When electrically activated, world-side switchable waveplate 1220rotates a polarization of world light 432 by 90 degrees such that, forexample, LVP light is converted to LHP light or LHP light is convertedto LVP light. When not electrically activated, world-side switchablewaveplate 1220 leaves world light 432 substantially unaltered.

In the illustrated embodiment, user-side shutter elements 1202 include auser-side polarizer 1214 and a user-side switchable waveplate 1218.User-side polarizer 1214 may be positioned closer to eyepiece 1212 andworld objects 430 such that virtual image light 423 and world light 432passes first through user-side polarizer 1214 prior to passing throughuser-side switchable waveplate 1218. Upon passing through user-sidepolarizer 1214, virtual image light 423 and world light 432 are linearlypolarized along a second axis perpendicular to the first axis.Accordingly, user-side polarizer 1214 may comprise a linear polarizerthat is perpendicular to world-side polarizer. After passing throughuser-side polarizer 1214, virtual image light 423 and world light 432pass through a first layer of lens assembly 1208. As described herein,the first layer of lens assembly 1208 may apply optical power to thelight passing therethrough. After passing through the first layer oflens assembly 1208, virtual image light 423 and world light 432 passthrough user-side switchable waveplate 1214. When electricallyactivated, user-side switchable waveplate 1214 rotates a polarization ofvirtual image light 423 and world light 432 by 90 degrees such that, forexample, LVP light is converted to LHP light or LHP light is convertedto LVP light. When not electrically activated, user-side switchablewaveplate 1214 leaves virtual image light 423 and world light 432substantially unaltered.

After passing through user-side switchable waveplate 1218, virtual imagelight 423 and world light 432 pass through a second layer of lensassembly 1208. As described herein, the second layer of lens assembly1208 may apply optical power to the light passing therethrough so as tocancel or add to the optical power applied to the light when passingthrough the first layer. For example, the first and second layers oflens assembly 1208 may be configured such that, when user-sideswitchable waveplate 1218 is electrically activated, light passingthrough both layers is applied a non-zero net optical power and, whenuser-side switchable waveplate 1218 is not electrically activated, lightpassing through both layers is applied a zero net optical power, i.e.,is applied no net power. Accordingly, the first and second layers oflens assembly 1208 may be configured so as to apply a positive opticalpower to light having a first linear polarization and a negative opticalpower (with equal magnitude) to light having a second linearpolarization orthogonal to the first linear polarization.

In some embodiments, the first and second layers of lens assembly 1208are diffractive waveplate lenses. In some embodiments, lens assembly1208 may take the form of a different type of VFE, such as an LC Fresnellens, a deformable lens, or the like. In some embodiments, one or morecomponents of user-side shutter elements 1202 are considered to besubcomponents of lens assembly 1208 (i.e., are considered to be includedin lens assembly 1208). In one example, user-side polarizer 1214 isconsidered to be a subcomponent of lens assembly 1208. In anotherexample, user-side switchable waveplate 1218 is considered to be asubcomponent of lens assembly 1208. In another example, both user-sidepolarizer 1214 and user-side switchable waveplate 1218 are considered tobe subcomponents of lens assembly 1208. Example VFEs and other adaptivelens components, which may represent or be implemented as part of theone or more of the lens assemblies described herein, are described inU.S. patent application Ser. No. 15/902,927 filed on Feb. 22, 2018,published on Aug. 23, 2018 as U.S. Publication No. 2018/0239177, U.S.patent application Ser. No. 15/902,814 filed on Feb. 22, 2018, publishedon Aug. 23, 2018 as U.S. Publication No. 2018/0239147, U.S. patentapplication Ser. No. 15/933,297 filed on Mar. 22, 2018, published onSep. 27, 2018 as U.S. Publication No. 2018/0275394, and U.S. patentapplication Ser. No. 16/006,080 filed on Jun. 12, 2018, published onDec. 13, 2018 as U.S. Publication No. 2018/0356639, all of which areexpressly incorporated herein by reference in their entirety. Additionalexamples of such components are provided in U.S. Provisional PatentApplication No. 62/639,882, filed Mar. 7, 2018 (Attorney Docket No.MLEAP.180PR) and U.S. patent application Ser. No. 16/158,041 filed onOct. 11, 2018 (Attorney Docket No. MLEAP.183A), both of which are alsoexpressly incorporated herein by reference in their entirety.

FIG. 12B illustrates an example of display device 1200 operating inaccordance with a first state, according to some embodiments of thepresent disclosure. While operating in accordance with the first state,projector and injection optics 1222 are turned off, world-sideswitchable waveplate 1220 is electrically activated, and user-sideswitchable waveplate 1218 is not electrically activated. World light 432is first linearly polarized along a first axis by world-side polarizer1216. Thereafter, a polarization of world light 432 is rotated by 90degrees by world-side switchable waveplate 1220. Thereafter, world light432 is linearly polarized along a second axis perpendicular to the firstaxis by user-side polarizer 1214. Thereafter, a first layer of lensassembly 1208 applies a first optical power to world light 432.Thereafter, world light 432 passes through user-side switchablewaveplate 1218 substantially unaltered. Thereafter, a second layer oflens assembly 1208 applies a second optical power to world light 432equal in magnitude but opposite in sign to the first optical power,thereby canceling the first optical power. Thereafter, world light 432reaches the eye of the user.

FIG. 12C illustrates an example of display device 1200 operating inaccordance with a second state, according to some embodiments of thepresent disclosure. While operating in accordance with the second state,projector and injection optics 1222 are turned on, world-side switchablewaveplate 1220 is not electrically activated, and user-side switchablewaveplate 1218 is electrically activated. World light 432 impinging onworld-side polarizer 1216 is linearly polarized along a first axis byworld-side polarizer 1216. Thereafter, world light 432 passes throughworld-side switchable waveplate 1220 substantially unaltered.Thereafter, world light 432 is linearly polarized along a second axisperpendicular to the first axis by user-side polarizer 1214, causingworld light 432 to be completely or at least partially reduced, blocked,or dimmed. Concurrently, virtual image light 423 is projected onto oneor more waveguides of eyepiece 1212 by projector and injection optics1222. Thereafter, virtual image light 423 is outcoupled by eyepiece1212. Thereafter, virtual image light 423 is linearly polarized alongthe second axis by user-side polarizer 1214. Thereafter, a first layerof lens assembly 1208 applies a first optical power to virtual imagelight 423. Thereafter, a polarization of virtual image light 423 isrotated by 90 degrees by user-side switchable waveplate 1218.Thereafter, a second layer of lens assembly 1208 applies a secondoptical power to virtual image light 423 equal in magnitude and havingthe same sign as the first optical power, thereby doubling the appliedoptical power. Thereafter, virtual image light 423 reaches the eye ofthe user.

FIG. 13 illustrates a method 1300 of operating an optical system,according to some embodiments of the present disclosure. One or moresteps of method 1300 may be performed in a different order than theillustrated embodiment, and one or more steps of method 1300 may beomitted during performance of method 1300. In some embodiments, one ormore steps of method 1300 can be implemented as a computer-readablemedium or computer program product comprising instructions which, whenthe program is executed by one or more computers, cause the one or morecomputers to at least in part carry out some or all of the steps ofmethod 1300. Such computer program products can be transmitted, over awired or wireless network, in a data carrier signal carrying thecomputer program product.

At step 1302, light associated with a world object is received at theoptical system. At step 1304, the light associated with the world objectis linearly polarized along a first axis. At step 1306, it is determinedwhether the optical system is operating in accordance with a first stateor a second state. When the optical system is operating in accordancewith the first state, method 1300 proceeds to step 1308. When theoptical system is operating in accordance with the second state, method1300 proceeds to step 1314. At step 1308, a polarization of the lightassociated with the world object is rotated by 90 degrees. At step 1310,the light associated with the world object is linearly polarized along asecond axis perpendicular to the first axis. At step 1312, zero netoptical power is applied to the light associated with the world object.Thereafter, the light associated with the world object reaches the eyeof the user.

At step 1314, light associated with a virtual image is projected onto aneyepiece of the optical system. At step 1316, the light associated withthe virtual image is outcoupled by the eyepiece. At step 1318, the lightassociated with the world object and the light associated with thevirtual image are linearly polarized along the second axis. At step1320, a polarization of the light associated with the virtual image isrotated by 90 degrees. At step 1322, non-zero net optical power isapplied to the light associated with the virtual image. Thereafter, thelight associated with the virtual image reaches the eye of the user.

FIG. 14 illustrates a method 1400 of operating an optical system,according to some embodiments of the present disclosure. One or moresteps of method 1400 may be performed in a different order than theillustrated embodiment, and one or more steps of method 1400 may beomitted during performance of method 1400. One or more steps of method1400 may be combined with one or more steps of method 1300. At step1402, ambient light is detected by an ambient light sensor. At step1404, a shuttering frequency is determined based on the detected ambientlight. At step 1406, the optical system is caused to switch betweenoperation in accordance with a first state and operation in accordancewith a second state based on the shuttering frequency.

FIG. 15 illustrates an example performance of method 1400, according tosome embodiments of the present disclosure. The upper plot of FIG. 15shows detected ambient light intensity as a function of time (asdetected by, e.g., ambient light sensors 434, 534). The lower plot ofFIG. 15 shows state switching between a first state and a second stateas a function of time, with time being aligned with the upper plot. Attime T₁, a user of the optical system is in a shaded outdoor area andthe detected ambient light has a medium intensity. Based on the detectedambient light at time T₁, a first shuttering frequency is determined.Determining the shuttering frequency may include determining a firstperiod P₁, the duration that the optical system is operating inaccordance with the first state prior to switching to the second state,and a second period P₂, the duration that the optical system isoperating in accordance with the second state prior to switching to thefirst state. Alternatively or additionally, determining the shutteringfrequency may include determining the ratio P₁/P₂, among otherpossibilities. Between times T₁ and T₂, the optical system is caused toswitch between the first and second states based on the first shutteringfrequency.

At time T₂, the user of the optical system relocates to a low-lightindoor area and the detected ambient light has a low intensity. Based onthe detected ambient light at time T₂, a second shuttering frequency isdetermined having a higher ratio P₁/P₂ than the first shutteringfrequency. In other words, to improve user experience and not overly dimthe world light in low-light conditions, the shuttering frequency may beadjusted so as to increase the amount of time that world light isallowed to pass through the optical system. Between times T₂ and T₃, theoptical system is caused to switch between the first and second statesbased on the second shuttering frequency.

At time T₃, the user of the optical system relocates to an outdoor areawith direct sunlight and the detected ambient light has a highintensity. Based on the detected ambient light at time T₃, a thirdshuttering frequency is determined having a lower ratio P₁/P₂ than boththe first and second shuttering frequencies. In other words, to improveuser experience and reduce the world light in high-light conditions, theshuttering frequency may be adjusted so as to decrease the amount oftime that world light is allowed to pass through the optical system.After time T₃, the optical system is caused to switch between the firstand second states based on the third shuttering frequency.

FIG. 16A illustrates an example of a display device 1600 operating inaccordance with a first state, according to some embodiments of thepresent disclosure. Display device 1600 may include one or morecomponents that are functionally equivalent or similar to one or more ofthose described above with reference to FIGS. 4A-4C, 5, 11A-11D, and/or12A-12C. For example, display device 1600 may have a single adaptivelens assembly 1605 on the user side of an eyepiece 1602 (the side ofeyepiece 1602 closest to the eye of the user). Lens assembly 1605 mayinclude a VFE assembly and may be configured to apply positive,negative, or zero optical power to the light passing through it. Displaydevice 1600 may include a shutter element 1603 coupled to the world sideof eyepiece 1602 (the side of eyepiece 1602 furthest from the eye of theuser and closest to world objects). While operating in accordance withthe first state, a controller 1620 causes a projector 1614 to be turnedoff, lens assembly 1605 to be inactive, and shutter element 1603 to beopen. When shutter element 1603 is open (i.e., electrically activated),world light 432 passing therethrough is substantially unaltered. Whenlens assembly 1605 is inactive, lens assembly 1605 imparts zero netoptical power to light (e.g., world light 432) passing therethrough.Accordingly, while operating in accordance with the first state, worldlight 432 may be presented to the user substantially unaltered. Asdescribed in further detail below, in some examples, display device 1600may hold/maintain the first state for an extended period of time (e.g.,indefinitely or until display device 1600 is required to present virtualcontent to the user).

FIG. 16B illustrates an example of display device 1600 operating inaccordance with a second state, according to some embodiments of thepresent disclosure. While operating in accordance with the second state,controller 1620 causes projector 1614 to be turned on, lens assembly1605 to be active, and shutter element 1603 to be closed. When shutterelement 1603 is closed (i.e., not electrically activated), world light432 passing therethrough is substantially blocked. When projector 1614is turned on, virtual image light 423 is projected onto eyepiece 1602and is thereafter outcoupled by eyepiece 1602 toward the eye of theuser. When lens assembly 1605 is active, lens assembly 1605 impartsnonzero net optical power to light (e.g., virtual image light 423)passing therethrough. Accordingly, while operating in accordance withthe second state, display device 1600 may present virtual content to theuser that is perceived by the user as being positioned at one or more ofvarious possible depths. As described in further detail below, in someexamples, display device 1600 may hold/maintain the second state for anextended period of time (e.g., indefinitely or until display device 1600is required to provide the user with a view of the environment). In someembodiments, display device 1600 may synchronously control the shutterelement 1603 and the lens assembly 1605 so as to rapidly alternatebetween the first and second states at a particular rate or frequency.

FIG. 16C illustrates an example of display device 1600 operating inaccordance with a third state, according to some embodiments of thepresent disclosure. While operating in accordance with the third state,controller 1620 causes projector 1614 to be turned on, lens assembly1605 to be inactive, and shutter element 1603 to be open. When shutterelement 1603 is open (i.e., electrically activated), world light 432passing therethrough is substantially unaltered. When projector 1614 isturned on, virtual image light 423 is projected onto eyepiece 1602 andis thereafter outcoupled by eyepiece 1602 toward the eye of the user.When lens assembly 1605 is inactive, lens assembly 1605 imparts zero netoptical power to light (e.g., world light 432 and/or virtual image light423) passing therethrough. Accordingly, while operating in accordancewith the third state, display device 1600 may present virtual content tothe user that is perceived by the user as being positioned at opticalinfinity.

As such, in the third state, display device 1600 need not activate lensassembly 1605 while injecting light representing virtual content atoptical infinity into eyepiece 1602, and may therefore allow light fromthe real world to pass through toward the user without any issues. Asdescribed in further detail below, in some examples, display device 1600may hold/maintain the third state for an extended period of time (e.g.,indefinitely or until display device 1600 is required to present virtualcontent at less than optical infinity). In some embodiments, displaydevice 1600 may synchronously control the shutter element 1603 and thelens assembly 1605 to rapidly alternate between the second and thirdstates so as to rapidly present some virtual content at less thanoptical infinity and other virtual content at optical infinity. Similarto that described in reference to FIGS. 14 and 15, a shutteringfrequency of switching between the first state, the second state, and/orthe third state may be determined based on detected ambient light and/orthe desired brightness of the virtual content.

As mentioned above, in some embodiments, display device 1600 may notsynchronously control the shutter element 1603 and the lens assembly1605 so as to rapidly alternate between two or more states, but insteadmay selectively hold/maintain a single state (e.g., one of the firststate, second state, and third state) or otherwise control the shutterelement 1603 and the lens assembly 1605 independently for an extendedperiod of time. In at least some of these embodiments, display device1600 may be configured to alternate between at least two different modesof operation including (i) a first mode of operation in which displaydevice 1600 is configured to control a state of the shutter element 1603and a state of the lens assembly 1605 independently or in an otherwiseasynchronous manner, and (ii) a second mode of operation in whichdisplay device 1600 is configured to control the state of the shutterelement 1603 and a state of the lens assembly 1605 in a synchronousmanner. For example, in the first mode of operation, display device 1600may hold/maintain a single state (e.g., one of the first state, secondstate, and third state) or otherwise control the shutter element 1603and the lens assembly 1605 independently, and in the second mode ofoperation, display device 1600 may cause the shutter element 1603 andthe lens assembly 1605 to synchronously switch between two or morestates (e.g., two or more of the first state, second state, and thirdstate).

In some examples, in the first mode of operation, display device 1600may hold/maintain a state similar or equivalent to the second state foran extended period of time (e.g., indefinitely or until display device1600 is required to provide the user with a view of the environment). Inat least some such examples, the first mode of operation may correspondto a VR mode in which controller 1620 causes projector 1614 to be turnedon, lens assembly 1605 to be optionally active, and shutter element 1603to be closed or otherwise held in a relatively dim state. Optionally, inthe first mode of operation, controller 1620 may cause lens assembly1605 to switch states as needed to impart the appropriate amount ofoptical power to light from the projector. In the aforementionedexamples, controller 1620 may cause display device 1600 to switch intoand/or out of the first mode of operation based on any of a variety offactors, including user input (e.g., as indicated by data received fromone or more sensors, user interfaces, input devices, etc.), anapplication that is running on display device 1600, user preferences,sensor data, and the like. For instance, controller 1620 may switch intothe first mode of operation so as to initiate a VR experience in whichthe user is provided with little to no see-through visibility of theenvironment in front of them responsive to launching or terminatingexecution of a specific application on display device 1600, receivingindication that the user wishes to enter such a mode or exit anothermode based on input received through a handheld controller and/orgraphical user interface, and/or an occurrence of one or more otherevents. Similarly, controller 1620 may switch out of the first mode ofoperation so as to terminate a VR experience or transition to an AR ormixed reality (MR) experience in which the user is provided withincreased see-through visibility of the environment in front of themresponsive to launching or terminating execution of a specificapplication on display device 1600, receiving indication that the userwishes to exit a VR mode or enter another mode (e.g., an AR or MR mode)based on input received through a handheld controller and/or graphicaluser interface, and/or an occurrence of one or more other events. Otherconfigurations are possible.

In other examples, in the first mode of operation, display device 1600may hold/maintain a state similar or equivalent to the third state foran extended period of time (e.g., indefinitely or until display device1600 is required to present virtual content at less than opticalinfinity). In at least some such examples, the first mode of operationmay correspond to a mode in which controller 1620 causes projector 1614to be turned on, lens assembly 1605 to be held in a fixed state, andshutter element 1603 to be held open. Optionally, in the first mode ofoperation, controller 1620 may cause shutter element 1603 to switchbetween open and closed states. In the aforementioned examples,controller 1620 may cause display device 1600 to switch into and/or outof the first mode of operation based on any of a variety of factors,including a depth at which the user's eyes are determined to be fixated,a depth in front of the user at which virtual content is to be perceivedby the user, an accommodation-vergence mismatch for the virtual content,and the like. In some embodiments, controller 1620 may utilize data fromone or more inward-facing cameras (e.g., images of one or both of theuser's eyes) to determine the depth at which the user's eyes arefixated, evaluate the determined depth against a set of criteria, andswitch into and/or out of the first mode of operation based on theresults of the evaluation. For instance, in these embodiments,controller 1620 may determine whether an accommodation-vergence mismatchfor the virtual content exceeds one or more predetermined thresholdsbased at least in part on the depth at which the user's eyes aredetermined to be fixated, and may switch into and/or out of the firstmode of operation in response to a determination that theaccommodation-vergence mismatch for the virtual content exceeds one ormore predetermined thresholds. Example systems and techniques foradjusting the wavefront divergence of light representing virtual contentfor enhanced user perception, comfort, and/or experience, which mayrepresent or be implemented as part of one or more of the systems andtechniques described herein, are described in U.S. patent applicationSer. No. 15/430,277 filed on Feb. 10, 2017, published on Aug. 17, 2017as U.S. Publication No. 2017/0237974, U.S. patent application Ser. No.15/469,369 filed on Mar. 24, 2017, published on Sep. 28, 2019 as U.S.Publication No. 2017/0276948, U.S. patent application Ser. No.16/250,931 filed on Jan. 17, 2019, published on Aug. 8, 2019 as U.S.Publication No. 2019/0243448, U.S. patent application Ser. No.16/353,989 filed on Mar. 14, 2019, published on Oct. 10, 2019 as U.S.Publication No. 2019/0311527, and U.S. patent application Ser. No.16/389,529 filed on Apr. 19, 2019, published on Oct. 24, 2019 as U.S.Publication No. 2019/0324276, all of which are expressly incorporatedherein by reference in their entirety. In some embodiments, one or moreof such systems and techniques described in one or more of theaforementioned patent applications may represent or be implemented aspart of one or more of systems and techniques for switching into and/orout of the first mode of operation. Other configurations are possible.

In the second mode of operation, controller 1620 of display device 1600may cause the shutter element 1603 and the lens assembly 1605 tosynchronously switch between different states in a manner yielding aninverse relationship between the amount of ambient light from theenvironment of the user allowed by shutter assembly 1603 to passtherethrough toward the user and the amount of wavefront divergenceimparted by lens assembly 1605 to light passing therethrough toward theuser. For example, in the second more of operation, controller 1620 ofdisplay device 1600 may cause the shutter element 1603 and the lensassembly 1605 to synchronously switch between two states that aresimilar or equivalent to the first and second states as described abovein reference to FIGS. 16A and 16B, respectively, or may cause theshutter element 1603 and the lens assembly 1605 to synchronously switchbetween two states that are similar or equivalent to the second andthird states as described above in reference to FIGS. 16B and 16C,respectively.

FIG. 17 illustrates a simplified computer system 1700 according to anembodiment described herein. Computer system 1700 as illustrated in FIG.17 may be incorporated into devices described herein. FIG. 17 provides aschematic illustration of one embodiment of computer system 1700 thatcan perform some or all of the steps of the methods provided by variousembodiments. It should be noted that FIG. 17 is meant only to provide ageneralized illustration of various components, any or all of which maybe utilized as appropriate. FIG. 17, therefore, broadly illustrates howindividual system elements may be implemented in a relatively separatedor relatively more integrated manner.

Computer system 1700 is shown comprising hardware elements that can beelectrically coupled via a bus 1705, or may otherwise be incommunication, as appropriate. The hardware elements may include one ormore processors 1710, including without limitation one or moregeneral-purpose processors and/or one or more special-purpose processorssuch as digital signal processing chips, graphics accelerationprocessors, and/or the like; one or more input devices 1715, which caninclude without limitation a mouse, a keyboard, a camera, and/or thelike; and one or more output devices 1720, which can include withoutlimitation a display device, a printer, and/or the like.

Computer system 1700 may further include and/or be in communication withone or more non-transitory storage devices 1725, which can comprise,without limitation, local and/or network accessible storage, and/or caninclude, without limitation, a disk drive, a drive array, an opticalstorage device, a solid-state storage device, such as a random accessmemory (“RAM”), and/or a read-only memory (“ROM”), which can beprogrammable, flash-updateable, and/or the like. Such storage devicesmay be configured to implement any appropriate data stores, includingwithout limitation, various file systems, database structures, and/orthe like.

Computer system 1700 might also include a communications subsystem 1719,which can include without limitation a modem, a network card (wirelessor wired), an infrared communication device, a wireless communicationdevice, and/or a chipset such as a Bluetooth™ device, an 802.11 device,a WiFi device, a WiMax device, cellular communication facilities, etc.,and/or the like. The communications subsystem 1719 may include one ormore input and/or output communication interfaces to permit data to beexchanged with a network such as the network described below to name oneexample, other computer systems, television, and/or any other devicesdescribed herein. Depending on the desired functionality and/or otherimplementation concerns, a portable electronic device or similar devicemay communicate image and/or other information via the communicationssubsystem 1719. In other embodiments, a portable electronic device, e.g.the first electronic device, may be incorporated into computer system1700, e.g., an electronic device as an input device 1715. In someembodiments, computer system 1700 will further comprise a working memory1735, which can include a RAM or ROM device, as described above.

Computer system 1700 also can include software elements, shown as beingcurrently located within the working memory 1735, including an operatingsystem 1740, device drivers, executable libraries, and/or other code,such as one or more application programs 1745, which may comprisecomputer programs provided by various embodiments, and/or may bedesigned to implement methods, and/or systems, provided by otherembodiments, as described herein. Merely by way of example, one or moreprocedures described with respect to the methods discussed above, mightbe implemented as code and/or instructions executable by a computerand/or a processor within a computer; in an aspect, then, such codeand/or instructions can be used to and/or adapt a general purposecomputer or other device to perform one or more operations in accordancewith the described methods.

A set of these instructions and/or code may be stored on anon-transitory computer-readable storage medium, such as the storagedevice(s) 1725 described above. In some cases, the storage medium mightbe incorporated within a computer system, such as computer system 1700.In other embodiments, the storage medium might be separate from acomputer system e.g., a removable medium, such as a compact disc, and/orprovided in an installation package, such that the storage medium can beused to program, configure, and/or adapt a general purpose computer withthe instructions/code stored thereon. These instructions might take theform of executable code, which is executable by computer system 1700and/or might take the form of source and/or installable code, which,upon compilation and/or installation on computer system 1700 e.g., usingany of a variety of generally available compilers, installationprograms, compression/decompression utilities, etc., then takes the formof executable code.

It will be apparent to those skilled in the art that substantialvariations may be made in accordance with specific requirements. Forexample, customized hardware might also be used, and/or particularelements might be implemented in hardware, software including portablesoftware, such as applets, etc., or both. Further, connection to othercomputing devices such as network input/output devices may be employed.

As mentioned above, in one aspect, some embodiments may employ acomputer system such as computer system 1700 to perform methods inaccordance with various embodiments of the technology. According to aset of embodiments, some or all of the procedures of such methods areperformed by computer system 1700 in response to processor 1710executing one or more sequences of one or more instructions, which mightbe incorporated into the operating system 1740 and/or other code, suchas an application program 1745, contained in the working memory 1735.Such instructions may be read into the working memory 1735 from anothercomputer-readable medium, such as one or more of the storage device(s)1725. Merely by way of example, execution of the sequences ofinstructions contained in the working memory 1735 might cause theprocessor(s) 1710 to perform one or more procedures of the methodsdescribed herein. Additionally or alternatively, portions of the methodsdescribed herein may be executed through specialized hardware.

The terms “machine-readable medium” and “computer-readable medium,” asused herein, refer to any medium that participates in providing datathat causes a machine to operate in a specific fashion. In an embodimentimplemented using computer system 1700, various computer-readable mediamight be involved in providing instructions/code to processor(s) 1710for execution and/or might be used to store and/or carry suchinstructions/code. In many implementations, a computer-readable mediumis a physical and/or tangible storage medium. Such a medium may take theform of a non-volatile media or volatile media. Non-volatile mediainclude, for example, optical and/or magnetic disks, such as the storagedevice(s) 1725. Volatile media include, without limitation, dynamicmemory, such as the working memory 1735.

Common forms of physical and/or tangible computer-readable mediainclude, for example, a floppy disk, a flexible disk, hard disk,magnetic tape, or any other magnetic medium, a CD-ROM, any other opticalmedium, punchcards, papertape, any other physical medium with patternsof holes, a RAM, a PROM, EPROM, a FLASH-EPROM, any other memory chip orcartridge, or any other medium from which a computer can readinstructions and/or code.

Various forms of computer-readable media may be involved in carrying oneor more sequences of one or more instructions to the processor(s) 1710for execution. Merely by way of example, the instructions may initiallybe carried on a magnetic disk and/or optical disc of a remote computer.A remote computer might load the instructions into its dynamic memoryand send the instructions as signals over a transmission medium to bereceived and/or executed by computer system 1700.

The communications subsystem 1719 and/or components thereof generallywill receive signals, and the bus 1705 then might carry the signalsand/or the data, instructions, etc. carried by the signals to theworking memory 1735, from which the processor(s) 1710 retrieves andexecutes the instructions. The instructions received by the workingmemory 1735 may optionally be stored on a non-transitory storage device1725 either before or after execution by the processor(s) 1710.

The methods, systems, and devices discussed above are examples. Variousconfigurations may omit, substitute, or add various procedures orcomponents as appropriate. For instance, in alternative configurations,the methods may be performed in an order different from that described,and/or various stages may be added, omitted, and/or combined. Also,features described with respect to certain configurations may becombined in various other configurations. Different aspects and elementsof the configurations may be combined in a similar manner. Also,technology evolves and, thus, many of the elements are examples and donot limit the scope of the disclosure or claims.

Specific details are given in the description to provide a thoroughunderstanding of exemplary configurations including implementations.However, configurations may be practiced without these specific details.For example, well-known circuits, processes, algorithms, structures, andtechniques have been shown without unnecessary detail in order to avoidobscuring the configurations. This description provides exampleconfigurations only, and does not limit the scope, applicability, orconfigurations of the claims. Rather, the preceding description of theconfigurations will provide those skilled in the art with an enablingdescription for implementing described techniques. Various changes maybe made in the function and arrangement of elements without departingfrom the spirit or scope of the disclosure.

Also, configurations may be described as a process which is depicted asa schematic flowchart or block diagram. Although each may describe theoperations as a sequential process, many of the operations can beperformed in parallel or concurrently. In addition, the order of theoperations may be rearranged. A process may have additional steps notincluded in the figure. Furthermore, examples of the methods may beimplemented by hardware, software, firmware, middleware, microcode,hardware description languages, or any combination thereof. Whenimplemented in software, firmware, middleware, or microcode, the programcode or code segments to perform the necessary tasks may be stored in anon-transitory computer-readable medium such as a storage medium.Processors may perform the described tasks.

Having described several example configurations, various modifications,alternative constructions, and equivalents may be used without departingfrom the spirit of the disclosure. For example, the above elements maybe components of a larger system, wherein other rules may takeprecedence over or otherwise modify the application of the technology.Also, a number of steps may be undertaken before, during, or after theabove elements are considered. Accordingly, the above description doesnot bind the scope of the claims.

As used herein and in the appended claims, the singular forms “a”, “an”,and “the” include plural references unless the context clearly dictatesotherwise. Thus, for example, reference to “a user” includes a pluralityof such users, and reference to “the processor” includes reference toone or more processors and equivalents thereof known to those skilled inthe art, and so forth.

Also, the words “comprise”, “comprising”, “contains”, “containing”,“include”, “including”, and “includes”, when used in this specificationand in the following claims, are intended to specify the presence ofstated features, integers, components, or steps, but they do notpreclude the presence or addition of one or more other features,integers, components, steps, acts, or groups.

It is also understood that the examples and embodiments described hereinare for illustrative purposes only and that various modifications orchanges in light thereof will be suggested to persons skilled in the artand are to be included within the spirit and purview of this applicationand scope of the appended claims.

What is claimed is:
 1. A method of operating an optical system, themethod comprising: receiving light associated with a world object;linearly polarizing the light associated with the world object along afirst axis; when the optical system is operating in accordance with afirst state: rotating a polarization of the light associated with theworld object; and linearly polarizing the light associated with theworld object along a second axis perpendicular to the first axis; whenthe optical system is operating in accordance with a second state:projecting light associated with a virtual image onto an eyepiece; andlinearly polarizing the light associated with the world object and thelight associated with the virtual image along the second axis.
 2. Themethod of claim 1, further comprising: rotating a polarization of thelight associated with the virtual image when the optical system isoperating in accordance with the second state.
 3. The method of claim 1,further comprising: applying zero net optical power to the lightassociated with the world object when the optical system is operating inaccordance with the first state.
 4. The method of claim 1, furthercomprising: applying non-zero net optical power to the light associatedwith the virtual image when the optical system is operating inaccordance with the second state.
 5. The method of claim 1, furthercomprising: outcoupling the light associated with the virtual image whenthe optical system is operating in accordance with the second state. 6.An optical system comprising: one or more world-side shutter elementsconfigured to: linearly polarize light associated with a world objectalong a first axis; and rotate a polarization of the light associatedwith the world object when the optical system is operating in accordancewith a first state; an eyepiece coupled to the one or more world-sideshutter elements; a projector configured to project light associatedwith a virtual image onto the eyepiece when the optical system isoperating in accordance with a second state; and one or more user-sideshutter elements coupled to the eyepiece and configured to: linearlypolarize the light associated with the world object along a second axisperpendicular to the first axis when the optical system is operating inaccordance with the first state; and linearly polarize the lightassociated with the world object and the light associated with thevirtual image along the second axis when the optical system is operatingin accordance with the second state.
 7. The optical system of claim 6,wherein the one or more user-side shutter elements are furtherconfigured to: rotate a polarization of the light associated with thevirtual image when the optical system is operating in accordance withthe second state.
 8. The optical system of claim 6, further comprising:a lens assembly coupled to the one or more user-side shutter elements.9. The optical system of claim 8, wherein the lens assembly isconfigured to apply zero net optical power to the light associated withthe world object when the optical system is operating in accordance withthe first state.
 10. The optical system of claim 8, wherein the lensassembly is configured to apply non-zero net optical power to the lightassociated with the virtual image when the optical system is operatingin accordance with the second state.
 11. The optical system of claim 6,wherein the eyepiece is configured to outcouple the light associatedwith the virtual image toward the one or more user-side shutter elementswhen the optical system is operating in accordance with the secondstate.
 12. The optical system of claim 6, wherein: the one or moreworld-side shutter elements includes: a world-side polarizer; and aworld-side switchable waveplate; and the one or more user-side shutterelements includes: a user-side polarizer; and a user-side switchablewaveplate.
 13. The optical system of claim 12, wherein the opticalsystem is operating in accordance with the first state when theworld-side switchable waveplate is electrically activated and theuser-side switchable waveplate is not electrically activated.
 14. Theoptical system of claim 12, wherein the optical system is operating inaccordance with the second state when the user-side switchable waveplateis electrically activated and the world-side switchable waveplate is notelectrically activated.
 15. The optical system of claim 12, wherein theworld-side polarizer is coupled to the world-side switchable waveplate.16. An optical system comprising: a projector configured to emit light;at least one waveguide optically coupled to the projector and configuredto receive and redirect light therefrom toward a user; a shutterassembly comprising at least one component positioned adjacent to the atleast one waveguide, wherein the shutter assembly is selectivelyswitchable between different states in which the shutter assembly isconfigured to allow different amounts of ambient light from anenvironment of the user to pass therethrough toward the user,respectively; an adaptive lens assembly positioned between the at leastone waveguide and the user, wherein the adaptive lens assembly isselectively switchable between different states in which the adaptivelens assembly is configured to impart different amounts of wavefrontdivergence to light passing therethrough toward the user, respectively;and control circuitry communicatively coupled to the projector, theshutter assembly, and the adaptive lens assembly, wherein the controlcircuitry is configured to cause the shutter assembly and the adaptivelens assembly to synchronously switch between two or more states at aparticular rate, the two or more states comprising: a first state inwhich the shutter assembly is configured to allow a first amount ofambient light from the environment of the user to pass therethroughtoward the user and the adaptive lens assembly is configured to impart afirst amount of wavefront divergence to light passing therethrough; anda second state in which the shutter assembly is configured to allow asecond amount of ambient light from the environment of the user to passtherethrough toward the user and the adaptive lens assembly isconfigured to impart a second amount of wavefront divergence to lightpassing therethrough, wherein the second amount of ambient light isdifferent from the first amount of ambient light and the second amountof wavefront divergence is different from the first amount of wavefrontdivergence.
 17. The optical system of claim 16, wherein the secondamount of ambient light is less than the first amount of ambient lightand the second amount of wavefront divergence is greater than the firstamount of wavefront divergence.
 18. The optical system of claim 16,wherein the particular rate at which to cause the shutter assembly andthe adaptive lens assembly to synchronously switch between the two ormore states comprises a rate greater than or equal to a minimumswitching frequency.
 19. The optical system of claim 16, wherein in thesecond state, the control circuitry is configured to cause the projectorto emit light representing virtual content that is to be perceived bythe user as being positioned at a first depth in front of the user, andwherein the control circuitry is configured to determine at least one ofthe second amount of ambient light and the second amount of wavefrontdivergence based on the first depth in front of the user at whichvirtual content is to be perceived by the user.
 20. The optical systemof claim 16, wherein the at least one component of the shutter assemblycomprises at least one component positioned between the at least onewaveguide and the user.